The number of rape convictions in Wales has risen to a four-year high, according to figures revealed to the BBC.
The Crown Prosecution Service (CPS) in Wales said convictions had risen from 46.6% in 2006-7, to 59.3% in 2009-10.
However, Wales' police forces recorded 1,586 unsolved or "undetected" rapes out of 2,983 reported in the same period.
Rape charities say every effort is needed to boost detection rates.
Between 2006 and 2010, the CPS pursued 796 rape cases, with 57% resulting in conviction, according to the figures issued under the Freedom of Information Act.
The figures revealed to BBC Wales follow a major review in Wales and England earlier this year by Baroness Stern, which said a new approach was needed to give greater priority to the care and support of rape victims.
The Stern Review said debate had previously been too focused on rape conviction rates.
Yvonne Traynor, chief executive of Rape Crisis in England and Wales, who welcomed the improvements in conviction rates revealed in the figures, echoed that view.
She said although things were moving in the right direction, it was happening too slowly for those experiencing the trauma of rape.
Ms Traynor said: "Worryingly, the number of 'undetected' cases and the 'no crimed' cases need to be monitored to ensure that every case is taken seriously and every effort is made to ensure that all cases are treated with the same degree of diligence and investigation.
"However slowly this is happening I am pleased to see the statistics for rape convictions on the increase.
"Hopefully this means that the general public who sit on juries have more of an understanding of the nature of rape and the traumatic effect it has on survivors."
Dyfed Powys Police saw the biggest improvement in conviction rate with 63.6% of successful convictions in 2009-10, up from 46.2% in 2008-09.
Second was North Wales with 82.8%, up from 67.6%, followed by South Wales, up slightly at 55.3%, from 52.5%.
Gwent Police's conviction rate fell, with 55.1% in 2009-10, from 58.7% in 2008-09.
But Det Ch Insp Steve Mogg, who heads Gwent Police's Onyx unit for investigating rape and serious sexual abuse, said the force had made vast improvements recently and had a 74% conviction rate for the year to date.
Of the four police force areas in Wales, Dyfed Powys Police had the highest percentage of undetected rapes during the four-year period - at 70.9%.
A spokeswoman said they had continued to experience an improvement in the conviction rates for rape cases.
In 2008, 76.9% of the cases which proceeded to court resulted in a conviction, said the spokeswoman.
She added that the force was working closely with partner agencies such as the Crown Prosecution Service and other voluntary sector support and counselling agencies to improve its response and support for victims.
"We acknowledge that we must continue to improve," she added.
"A significant amount of work has been undertaken by the force and the other agencies which includes the training of specialist resources to provide the necessary response and support to victims at the earliest opportunities."
Gwent Police recorded 67.4% undetected rape cases, while South Wales Police had 41.5% undetected.
North Wales Police had the lowest percentage of undetected rapes, at 38.8%.
The force was the only one able to break down these figures further, explaining that out of those classed as detected, four were not pursued by the CPS, two saw the suspect die, one saw the victim or witness unwilling to prosecute and 22 were still the result of ongoing investigations, while 53 were investigated but it was found that no crime had taken place.
Det Supt Jane MacKay, of the public protection department of South Wales Police, said rape investigations were extremely complex and sometimes, even though every line of enquiry may be exhausted, there was not always sufficient evidence to prosecute.
South Wales Police has been placed in the top three nationally for detecting rape but was not resting on its laurels and would continue to pursue rape convictions "relentlessly", she added.
"We have achieved this level of national performance by working hard to ensure that every complaint of rape is thoroughly and professionally investigated.
"For example, we have a number of specialist officers who are available across the force 24/7 and are always deployed whenever an allegation of rape is received.
"We work with our criminal justice partners and take a proactive approach at every phase of the policing process, from investigation, to arrest, trial, and sentencing, and we strive to increase the confidence of rape victims so they feel empowered to deliver evidence and statements.
"Furthermore, our major crime review investigation team review every reported rape if the incident is still undetected after 28 days."
Frontline officers and detectives are currently receiving extra training to alert them to the importance of collecting potential DNA evidence as early as possible in the investigation.
Gwent's Det Ch Insp Mogg said solving rape crimes and securing convictions was a very difficult task.
He said: "When you bear in mind most rapes are committed by people known to the victim, it makes them very complex to investigate and try to prove guilt.
"We know who defendants are in 95% of cases but turning that into a straightforward prosecution is very complex."
Difficult to prosecute
He said the picture was improving since the Stern Review.
"Last year in the 12 months up to June 2009, the CPS in Gwent discontinued 35% of our cases, which is very high, but in the 12 months to June 2010, it was just 14.3%, a reduction of 21%, which is very pleasing.
"I think this is down to the fact we've got a specific team at the Onyx unit and it's seen more people going before the courts and more people standing trial since it was set up in 2009.
"We are now able to put far more robust cases before the Crown which helps more people be charged and convicted."
Kath Coleman, sexual offences specialist for CPS Gwent, said that although rape remained one of the most serious and damaging offences, there was no escaping the fact that it was also one of the most difficult to prosecute.
She said: "The CPS has been working closely alongside our partners in the police throughout Wales to improve the way we handle cases and, crucially, the service we provide to victims.
"Our efforts are starting to see results in terms of the number of rape cases that are taken to court.
"In Gwent, for example, over the space of a year we have seen a rise of 50% in the number of rape cases taken to court.
"Conviction rates for rape offences are improving, but we want to ensure that they keep improving."
Det Ch Insp Wayne Jones of North Wales Police's public protection unit said the force recently launched an action plan to boost conviction and detection rates.On Thursday, BBC News Online looks at the impact of sexual assault referral centres and how they are helping rape victims.