We estimate that on average, 55% of all people entering prison have a serious drug problem, but we are unable to give a robust and precise estimate of the number of prisoners who are addicted to class A drugs. A recent study reviewed 1,457 newly sentenced prisoners from 49 prisons. It showed that 62% of prisoners reported some drug use, and 41% of the sample reported heroin, cocaine powder or crack cocaine use during the four-week period prior to the study.