The light sensitivity of porphyria eutanea predisposes to an early ageing of the skin. In Atistralia where there is a high incidence of early ageing of the exposed shin, porphyria might easily remain undiagnosed.The classical manifestation of porphyria cutanea tarda, the traumatic blistering, is an intermittent phenomenon and appears only over exposed skin areas showing the clinical manifestations of actinic elastosis. The changes of the fine elastic fibres of the dermal papillae and the damaged basement membrane of the dermo-epidermal junetion predisposes the aged skin to dermo-epidermal blister formation. The ultimate cause of the blistering is not photo-sensitivity, but probably a toxic factor which further damages the dermo-epidermal connections without the intervention of inflammatory phenomena.Porphyria will cause blistering in aged shin, but various non-specific, non-diagnostic manifestations, due to photo-sensitivity occur in shin areas without elastotic changes.Cutaneous porphyria, as has been recently stressed by Donald et al., is not rare in Austraha. In recent years there have been very few clinical meetings of dermatology without presentation of examples of it. The condition, however, might have an even higher incidence than our clinical studies would indicate. As well as patients with classical skin manifestations which may be associated with the underlying biochem^ical deviations, there are many others in latency or remission.A relatively early ageing of the skin due to the increased sensitivity to sunlight attributed to the porphyrins, is one of the basic changes. Unfortunately early ageing of the exposed skin has such a high incidence in Austraha that it is not an indication to perform biochemical studies for the detection of porphyria. Eor example, the incidence of nodular elastoidosis of Favre and Eacouchot is so high in our geriatric age group that we would not think of the existence of porphyria to explain its presence in the individual case. In two patients of Ippen, this was the skin condition leading to the diagnosis of porphyria cutanea tarda (P.C.T.). In other countries a weatherbeaten skin with superficial, depigmented, irregular scarring would be at once suggestive of P.C.T. In Austraha the most likely explanation of this kind of changes on the face and hands is that they were produced by treatment of actinic keratoses and rodent carcinomas.There is an easy and inexpensive method to detect the real incidence of porphyria hepatica (P.H.) in a community. This consists in viewing the cut slices of the liver at autopsies under the Wood's light. The porphyric liver will show extensive fluorescence if exposed to this type of radiation. Using this method at 1300 unselected post-mortems, Ippen found a diffuse liver fluorescence in 14 and a more circumscribed tjrpe of fluorescence in more than 60 cases. The incidence of P.H. in his case material could be anything between 1% and 5%. Bielicki of Prague, very recently found in a similar study that 0-76% of the livers have shown fluorescence at aut...