Men feel more pain than women while recovering from major surgery, a study suggests.
More than 10,000 patients were monitored after operations, including heart or abdominal surgery, at a hospital in Germany.
Interviews with male and female patients, presented at the Euroanaesthesia conference, showed the men were reporting more pain.
Experts said gender differences in pain were still a disputed issue.
Hormones may play a role - the male sex hormone testosterone can reduce pain and women's pain thresholds are altered by the menstrual cycle.
Cultural and psychological factors are also thought to be involved.
The data from more than four years of surgeries involving 10,200 patients was collected at University Hospitals of the Ruhr University of Bochum in Germany.
The analysis showed there was no overall difference between the two genders' level of pain after an operation.
However, when the researchers divided the operations into major surgery and minor treatments, such as a biopsy, a pattern did emerge.
The male patients felt more pain after major surgery, while women were more likely to report pain after smaller procedures.
Dr Andreas Sandner-Kiesling, from the Medical University of Graz in Austria, said: "The influence of gender is a key issue in medicine.
"The gender differences on pain perception are still heavily disputed, both in experimental and clinical fields.
"Our data do not definitely clarify this issue, however, based on our findings it can be presumed that the type and severity of surgery may play a pivotal role, as females express higher pain scores after minor procedures, whereas males are more affected after major surgery."
Dr Beverly Collett, a consultant in pain management and anaesthesia at the University Hospital of Leicester NHS Trust, said: "The study titillates and makes you want to ask more questions, but doesn't allow you to probe it.
"Which procedures were classed as major surgery? How old were they? That will have an effect on sex hormones. And pain will be dependent on the parts of the body being biopsied."
She said women would report pain when heat was applied to the skin before men did, but that differences in pain perception were smaller than animal tests would suggest.
She said there was also a psychological component to pain, and men were known to "increase their ability to resist pain" when treated by young attractive female nurses compared with unattractive old male ones.
Meanwhile entrenched social values from childhood - boys told to get up after a fall, while girls were kissed better - also affected pain perception, she said.
"There's been a lot of dispute about pain in men and women, and this study does not clarify the issue."
Dr Edmund Keogh, a pain researcher at the University of Bath, commented: "There might be a difference between how men and women respond to analgesics, we don't know yet, we need to have lots more research."
He added that the overall picture on gender differences in pain was unclear: "The results are fairly inconsistent - some studies find differences, some don't and there's a lot of variability between them.
"Pain is hugely variable, but generally women are reporting more pain in comparison to men."
Dr Roman Cregg, from the University College London centre for anaesthesia, said: "Females are at increased risk for developing chronic pain conditions, they are more sensitive to painful stimuli in the laboratory settings compared with male subjects as well.
"According to the authors, overall, there was no difference between males and females in relation to the reported pain intensity, this is contrary to the majority of previously published experimental material.
"Ultimately the matter is complex."