Of 227 patients with psoriasis and rheumatic complaints, inflammatory arthritis was present in 168 patients, of whom 95 have been followed up for more than 5 years and 28 had been followed up for more than 10 years. In patients with psoriasis and inflammatory arthritis the majority were women, but in the Distal joint group, males predominated. The skin disease usually began on the arms and was restricted in extent, initially. It usually began before the arthritis. A few cases were apparently precipitated by trauma, but more by psychological factors. The course pursued by the skin lesions was generally favourable. The skin lesions were resistant to treatment in 20% of the patients. Puberty, pregnancy and the menopause had little effect on the skin lesions. Nail lesions were present in 80%, a greater frequency than that seen in uncomplicated psoriasis. These nail lesions began at a later age than the skin lesions, and commonly preceded the development of arthritis. There was a family history of psoriasis in 26% of first-degree relatives. A history of polyarthritis was obtained quite frequently, and of psoriatic arthritis in 3% of patients with Distal arthritis, and 2% of the Indistinguishable group. The arthritis was usually mild in degree. Ankylosing spondylitis occurred in 5% and sacro-iliitis in 19%. The sheep cell agglutination test for rheumatoid factor was negative in the majority of patients. It was positive in 16% and a fluctuating positive result was obtained in 10%.