Objectives. To establish whether patients with inflammatory arthritis plus psoriasis have a different outcome from those who do not have psoriasis. Methods. Seventy-nine patients with inflammatory arthritis plus psoriasis were recruited by the Norfolk Arthritis Register (NOAR) in 1990–94 and followed for 5 yrs. Their outcome was compared with the remainder (n = 755) of the NOAR cohort. We then restricted the analysis to subjects who were rheumatoid factor (RF)-negative, and compared those with and without psoriasis. Outcomes studied included remission, deformed joint count, the presence and extent of erosive damage and physical function. Results. Patients with psoriasis were younger, more likely to be male, less likely to be RF-positive and more likely to have been treated with disease-modifying drugs than patients without psoriasis. After adjustment for age, gender and treatment, the only differences between the psoriasis and non-psoriasis groups were in RF positivity (adjusted odds ratio 0.44; 95% CI 0.25, 0.78) and in the Larsen score in patients with erosions. Conclusions. Patients with inflammatory arthritis plus psoriasis have a similar outcome to other RF-negative patients with arthritis.