OBJECTIVES: : Temozolomide (TMZ) is an oral alkylating cytotoxic agent prescribed in monotherapy or in association with radiotherapy. TMZ is indicated in the treatment of high-grade brain tumours (glioblastoma multiforme and astrocytomas). However, TMZ is also used off-label. The main objective of this observational study was to assess the conformity of the use of TMZ in clinical practices. The secondary objective was to identify all indications in which TMZ was prescribed. METHODS: A French prospective multicenter study related to consecutive patients treated by TMZ was performed in 21 hospitals. Patients’ characteristics and drug prescriptions parameters, in terms of indications, dosages, treatment length, association with other drugs, side effects and prophylactic drugs, were collected. The level of conformity was analyzed in comparison with the market authorization and a prescription guideline elaborated by clinical experts and pharmacists. RESULTS: A total of 831 patients (median age 56 y; men: 57%) representing a total of 5982 TMZ cures were registered. TMZ was mainly prescribed in glioblastoma multiforme newly diagnosed or in relapse (51%), in anaplastic oligodendrogliomas (27%) and in anaplastic oligoastrocytomas (10%). TMZ was prescribed in malignant melanomas in 3% of cases. During monotherapy, the mean daily dose was 173 mg ± 35 mg/m². Ninety percent of patients received the planned duration of cycle. Thirty-three percent of side effects were observed. More than half of patients were co-treated by antiemetics (86%) and antiepileptics (63%). Indications were conformed to the guideline in 91% of cases but only in 54% in accordance with the market authorization. As compared to the market authorization, conformity rate was respectively observed in 76%, 84%, 90% 88% and 78% in terms of dosages, TMZ duration, cycle duration, associations, total length of treatment, leading to a global conformity of 54%. CONCLUSIONS: : In this study, TMZ prescription appears highly conform to the guideline but lower when compared to the market authorization.