Oral retinoid therapy has been considered for the prevention of skin carcinogenesis in humans, although animal studies have failed to provide any evidence of a protective effect of these drugs in the one-step photocarcinogenic system. In this study, oral therapy with vitamin A or a synthetic analogue, etretinate, was tested for ability to protect hairless mice (Skh-hr1) from the development of skin tumours following exposure to broad-band light (280-700 nm) for 25 weeks. Retinoids were given by gavage 3 times weekly either at low dosage (2000 IU vitamin A or 4 mg etretinate per kg body weight) or high dosage (10,000 IU vitamin A or 20 mg etretinate per kg body weight). None of the retinoid therapies compared to control mice (gavage vehicle only) modified skin tumour production in terms of time to onset of tumours, total tumour yield, or the types of tumours produced.