132 psoriasis patients who had been completely cleared with dithranol were assessed and then followed up over a 3-year period. The incubation time from specific incidents of stress to the development of psoriasis was between 2 days and 1 month. Specific stress within a month before the first attack was recalled by 51 patients (39%); chance association was excluded by studying a control group where there was significantly less specific stress. The prognosis for the psoriasis patients who recollected specific stress a month prior to the onset was significantly better than for the rest of the patients where none had been recalled.