OBJECTIVES: To estimate the cost-effectiveness of infliximab compared to usual treatment for treatment of active psoriatic arthritis (PSA) over five-years from a Canadian health care perspective. METHODS: A Markov computer simulation model representing the natural history of severe PSA patients was designed with a 16 week cycle length. Clinical states were defined based on number of active (swollen or tender) joints as follows: 1) zero joints; 2) 1-4 active joints; 3) 5-9 joints; and 4) = 10 joints. The model was stratified by baseline score on the psoriasis area and severity index (PASI) of RESULTS: At 5mg/kg dose, each infliximab infusion would cost $3661. The incremental cost and quality adjusted life years (QALYs) gained (95% CI) of the infliximab strategy were estimated to be $76,600 ($53,900-$97,400) and 1.01 (0.58-1.40), respectively. The incremental cost-effectiveness ratio was estimated to be $75,500 (95% CI $62,000-$100,100) per QALY gained. The model was robust to plausible parameter changes. CONCLUSIONS: Assuming a willingness to pay of $100,000 per QALY gained, our results show that for PSA patients similar to those included in the trials, adding infliximab may be economically attractive.