Plasma zinc, serum albumin and alkaline phosphatase (a zinc-dependent enzyme) were measured in thirty-five psoriatics and their age- and sex-matched controls. No significant difference was seen between these two groups as a whole, but psoriatics with less than 10% surface involvement had significantly higher mean plasma zinc levels than their respective control group. Psoriatic patients also showed a relationship between the extent of surface involvement and the plasma zinc level, those with more extensive involvement having lower levels than those with minimal involvement. The differences were not due to disturbances in serum albumin, and no abnormalities in serum alkaline phosphatase were observed.