A group of 53 patients initially participating in a phase I trial with the synthetic retinoid fenretinide was assessed for the long-term tolerability of this compound. The patients were evaluated after 42 months of drug intake at a dose of 200 mg/day, including a 3-day drug interruption at the end of each month, by the following examinations: a dermatological visit; an ophthalmological evaluation including an ophthalmological questionnaire and an electroretinogram (ERG); a study on blood chemistry and plasma retinol levels; a study on bone densities and on skeletal X-rays; and finally a psychological evaluation including various tests for anxiety, depression and overall mood. The results show that prolonged administration of fenretinide is well tolerated. No acute nor severe toxicity was observed and thus this compound can be considered a good candidate for chemoprevention trials in a variety of patient populations.