OBJECTIVE: To estimate the prevalence and causes of vitamin A deficiency disorders (VADD) in adult male prisoners in Nakuru, Kenya. METHODS: A total of 1048 male prisoners aged > or =16 years in Nakuru Government of Kenya prison in Nakuru, Kenya were examined by an ophthalmologist for signs of xerophthalmia. Two hundred and forty-one cases with xerophthalmia and 448 controls randomly selected from the remaining prison population were interviewed about risk factors for xerophthalmia and blood samples were taken to measure serum retinol and haemoglobin. RESULTS: 23.6% (95% CI = 21.1-26.3%) of examined inmates showed at least one sign of xerophthalmia, mostly night blindness (98.8% of cases). In the case-control study, the age-adjusted analyses showed that xerophthalmia was associated with age, length of imprisonment and previous imprisonment. Men with xerophthalmia were significantly more likely be in poor health characterised by significant illness, recent hospital admission, persistent cough, diarrhoea, fever or chronic illness. After multivariate adjustment, duration of imprisonment remained strongly associated with xerophthalmia (OR comparing >4 years with <6 months = 20.1, 95% CI = 8.3-48.8). Previous imprisonment, fever, diarrhoea, hospital admission and chronic illness were also significant predictors. Serum retinol levels were significantly lower in cases than controls, while there was no difference in haemoglobin levels. CONCLUSION: Vitamin A deficiency was a significant public health problem among these Kenyan male prisoners, indicating that it may be important in vulnerable groups other than young children and pregnant or lactating women.