Recent observations suggest the existence of trihexyphenidyl abuse linked to its hallucinogenic and euphoric effects. In order to determine the importance of this practice and the characteristics of those involved, a study based on data from the Provence-Alpes-Côte-d'Azur and the Corsica health reimbursement system was carried out. Individuals from these regions affiliated to the French health reimbursement system who had a prescription for trihexyphenidyl (Artane, Parkinane) reimbursed between January 1, 2001, and February 15, 2001, were selected. The delivery of prescriptions was monitored over a 9-month period. In total, 3028 subjects were selected. A subgroup comprising 2.1% of subjects with deviant behaviour was identified by factorial analysis and compared with the subgroup without deviant behaviour. The subjects with deviant behaviour were young and mostly male. The dosage of trihexyphenidyl was higher in these subjects (28 mg/day versus 7 mg/day) and a greater proportion used benzodiazepine and high-dose buprenorphine compared with those without deviant behaviour. The number of prescriptions delivered was higher (23.0 versus 7.7) as well the number of different physicians (4.9 versus 1.5) and pharmacies (5.0 versus 1.3) for those subjects with deviant behaviour. This study confirms the abuse and dependence potential associated with trihexyphenidyl use and the need to increase the supervision of this drug.