Trihexyphenidyl (THP) and other antiparkinsonian drugs are known to be substances of abuse. This is true both in abusers of other substances and in chronic schizophrenics, the latter being infrequent abusers of other drugs. Most reports on the abuse of antiparkinsonian drugs among schizophrenic patients warn against the possible harm of this self-medication. The present article describes the different effects of THP on both schizophrenic and non-schizophrenic abusers. The subjective experience in most chronic schizophrenic patients who abuse THP is positive: they claim that THP makes them feel and function better. In the light of these findings, the author suggests that research on the possible benefits of THP in contrast to the potential harm in chronic, residual schizophrenic patients is warranted.