In a population-based, matched case-control study from the South Swedish Health Care Region, which has the highest risk for melanoma in Sweden, the relation between the use of sunbeds or sunlamps and malignant melanoma was investigated. Between July 1, 1988, and June 30, 1990, a total of 400 melanoma patients and 640 healthy controls aged 15-75 years answered a comprehensive questionnaire containing different epidemiologic variables. Questions regarding the use of sunbeds or sunlamps were included. The odds ratio for developing malignant melanoma after ever having used sunbeds or sunlamps was 1.3. Considering all age groups, the odds ratio was significantly elevated after exposure more than 10 times a year to sunbeds or sunlamps (odds ratio (OR) = 1.8). When the study was restricted to patients and controls younger than age 30 years because the use of tanning devices is much more common among young persons, the odds ratio was higher (OR = 7.7 for more than 10 times a year vs. none). These findings were independent of constitutional factors and factors regarding sun exposure. A dose-response relation was evident. Furthermore, among melanoma patients in this young age group, the ratio of females to males was significantly higher than in older patients. When different melanoma presentation sites were considered, only lesions of the trunk were significantly associated with sunbed or sunlamp use (OR = 4.2 for more than 10 times a year vs. none).