A prospective study was conducted to assess general practitioners' diagnostic skills in a referral setting. The primary objective was to identify general practitioners' strengths and weaknesses in diagnosing a broad spectrum of skin conditions. The diagnoses of 315 skin conditions made by 165 general practitioners were compared with a reference standard. The reference standard was made up of 73 histopathological diagnoses, 119 dermatologists' clinical diagnoses and 123 dermatologists' diagnoses plus follow up. The diagnoses assigned by referring general practitioners were consistent with dermatologists' clinical diagnoses and histology (where available) in 57% of cases. General practitioners made the correct diagnosis in 44% of cases when compared with histopathology. General practitioners were generally good at diagnosing conditions such as acne, warts, rosacea, molluscum contagiosum, vitiligo and skin tags. The proportion of correct diagnoses for premalignant and malignant skin tumours was 47%, and that of skin rashes requiring a diagnosis was 44%. Further education of general practitioners would help to improve their diagnostic skills in certain skin conditions.