A study was carried out involving 172 patients with acne which warranted treatment with isotretinoin. Patients were followed up for between 12 and 41 months after discontinuation of treatment and the number of relapses was assessed. 37 patients (21%) relapsed. These relapses were correlated with patients' age, length of disease progression prior to treatment, total dose received, daily dose, duration of treatment and severity of acne. It appeared that only young age and severity of acne influenced the percentage of relapse.