It is generally accepted that the spine is the site of predilection for retinoid-induced skeletal abnormalities. However, the reported prevalence of skeletal problems varies widely. To investigate the frequency and severity of retinoid-induced spinal abnormalities, all records of patients who underwent spinal radiographs at the request of the department of dermatology between 1983 and 1993 were reviewed. This group of 135 patients comprised the total population of retinoid-treated patients and those patients who were investigated for possible future retinoid treatment. The mean treatment period in the total group was 30 months and the mean cumulative dose of retinoid was 31 g. In 50 patients the treatment period was > or = 24 months with 30 patients being treated for more than 48 months. Baseline radiographs were available from 26 patients and these were compared with the most recent X-rays during treatment. The mean treatment period in this 'prospective group' was 25 months and the mean cumulative dose of retinoid was 25 g. The prevalence of diffuse idiopathic skeletal hyperostosis (DISH), degenerative changes and osteoporosis in the total group was respectively 16%, 53% and 29%. There was no statistically significant relation between the duration of treatment or the cumulative dose and the prevalence or severity of DISH, degenerative changes and osteoporosis. Only the age of the patients was significantly related to the frequency and severity of skeletal abnormalities. In the 'prospective group', again, no important changes were observed between the radiographs at baseline and during treatment. In this study no relation whatsoever between spinal abnormalities and prolonged oral retinoid treatment could be established. The performance of annual routine spinal radiographs during retinoid treatment is not necessary in our opinion. Additional controlled and prospective studies on spinal and extraspinal skeletal abnormalities are required to develop definitive screening guidelines for patients submitted to long-term retinoid treatment.