OBJECTIVE: To obtain monetary valuations of the disutility associated with mild and moderate adverse effects (AE) of drug treatments for reumathoidic arthritis (RA). METHODS: Four frequent AE for the treatments of RA (rush, mild gastrointestinal disorders, vomiting and headache) were defined with the help of a focus group with RA patients. Later, 175 individuals randomly selected from a Spanish community were personally surveyed with the help of a questionnaire. Respondents were first asked to rank the AE by order of disutility. Then, the WTP for a reduction of the probability of each AE (by 100, 80 and 50 per cent), as well as for avoiding the symptoms of RA was assessed. The disutility of the AE in relation to the symptoms of RA was assessed by means of the standard gamble approach. The consistency of the results was tested by comparing the direct rankings with those derived from the WTP and standard gamble exercises. RESULTS: The average WTP for avoiding the AE in thousand PTA. per year was: rush, 24.6; vomiting, 43.3; headache, 45.7; and gastrointestinal disorders, 63.1. Consistency was very high in the WTP, 96.8% and 79.1% in the case of the standard gamble. In the case of rush, the WTP for different risks reductions (100, 80 and 50%) the consistency was 98.26%, 90.17% and 79.19% respectively. CONCLUSION: the avoidance of AE is becoming an increasingly important feature of innovative treatments. Generic utility measures of health are often not sensitive enough to adequately quantify the disutility of mild AE. WTP seems to provide a valid alternative, which shows a higher degree of consistency than the often recommended standard gamble approach.