Phenothiazines can give rise to serious and sometimes irreversible dermatological and oculotoxic side effects. These effects can take the form of photosensitivity, grey-purple discoloration and hyperpigmentation of the skin and hyperpigmentation of the conjunctiva, cornea, lens, retina, choroidea and macula. Involvement of the retina or macula can lead to impaired vision, blurred vision, disturbed colour perception and night blindness. We describe the mechanisms that are currently believed to underlie these side-effects. We advise annual ophthalmic monitoring of patients receiving long-term treatment with phenothiazianes.