Introduction excerpt: Robust clinical, biomedical, and public health efforts currently address chronic conditions such as heart disease, diabetes, and cancer. However, similar efforts are less common for nonfatal conditions such as psoriasis, which is estimated to affect between 1% and 3% of the adult population, and psoriatic arthritis, an inflammatory arthritis found in up to one third of adults with psoriasis. Both diseases present a substantial public health burden in terms of healthcare costs ($650 million in 1997); employment and ability to work; and quality of life.