Legal highs dealer: Deaths, crime rates will go up
From midnight on Wednesday 25 May it will be against the law in the UK to make or supply so-called "legal highs".
With names like Spice, Mamba and Annihilation, they're psychoactive chemicals created to mimic the effect of illegal drugs like cannabis and cocaine.
They used to be on sale in "head shops" on the high street, but the government says they can be deadly and need to be banned.
But will the ban stop the trade or drive it underground?
Mark has been supplying these drugs for eight years and he told the BBC what he thinks will happen now.