Clinicians have become increasingly aware of the important effects of psoriasis on patients' quality of life. As a result, several measures of the disabilities and handicaps associated with psoriasis have been developed. The Psoriasis Disability Index (PDI) has been shown to be sensitive to changes in the extent of lesions and to co-vary with the Sickness Impact Profile, a more general measure of the effects of disease on quality of life. In this study, patients with psoriasis and patients with other skin diseases completed the PDI. Although most items on the PDI were specific to psoriasis, some items applied to patients with urticaria, eczema, melanomas and other skin diseases. A factor analysis of the items indicated that the PDI contained two subscales, one concerning most aspects of everyday activities, the other concerning specific public situations such as the use of communal facilities.