OBJECTIVE The aim was to examine the effects of fertility drugs on malignant melanoma risk using data from the largest cohort of infertile women to date. METHODS A cohort of 54,362 women with infertility problems referred to Danish fertility clinics in the period 1963-1998 was established. A detailed data collection including information about type and amount of treatment was conducted. Using case-cohort techniques, we calculated rate ratios (RRs) of malignant melanoma associated with different fertility drugs after adjustment for parity status. RESULTS 112 malignant melanomas were identified during follow-up through 2000. Use of clomiphene, gonadotrophins, hCG or GnRH did not affect risk of malignant melanoma significantly. When stratifying for parity, however, use of gonadotrophins (RR = 2.29; CI: 1.16-4.52) or GnRH (RR = 3.26; 95% CI: 1.50-7.09) among parous women was associated with a significant increased risk. For all groups of fertility drugs, we found no association with number of cycles of use or years since first use (latency). CONCLUSIONS Our findings showed no strong association between malignant melanoma risk and use of fertility drugs, although the results indicated that use of gonadotrophins or GnRH might increase risk in parous women. Longer follow-up is needed to confirm our findings.