Trihexyphenidyl (THP) and other anticholinergics are liable to abuse by schizophrenic patients. Data concerning the incidence and characteristics of the abusers are scarce. In the present study an evaluation of 214 consecutive admissions of schizophrenic patients revealed 14 THP abusers, an incidence of 6.5%. The demographic and clinical variables of the THP abusers were compared with a randomized control group of 28 schizophrenic patients using the four-dimensional factors of the BPRS (Brief Psychiatric Rating Scale). No significant differences were found in demographic variables and comorbidity for antisocial personality disorder and other substances abuse. On admission, a trend towards more negative symptoms was detected among abusers. At discharge abusers had significantly higher mean BPRS scores and higher scores on the dimensional factor of hostile-suspiciousness. The results suggest that THP abuse is not rare among schizophrenic patients who may abuse anticholinergic agents to relieve negative symptoms and/or drug-induced Parkinsonism, or alternatively for its non-specific stimulant effects, on account of worsening of positive symptoms.