Smith-Lemli-Opitz (SLO) affected children have multiple congenital physical and mental abnormalities; photosensitivity to ultraviolet A (UVA) has recently become a recognized feature. We present a patient with SLO and prominent photosensitivity in whom detailed phototesting has been performed at baseline and following 6 months of cholesterol supplementation. There was significant improvement in the symptoms of photosensitivity, confirmed objectively by phototesting and accompanied by partial correction of the biochemical abnormalities seen in SLO. This case report is the first to show that cholesterol supplementation in SLO can lead to an objective improvement in the associated photosensitivity.