Before 1955, the incidence of malignant melanoma in Nordic countries increased from birth to approximately 30 years of age, when it levelled off to around five cases per 100 000 person-years. From 1957 onwards, the incidence no longer stabilized at the age of 30 years, but continued to increase with age to at least 100 cases per 100 000 person-years. The aims of this study were to examine this sudden change in melanoma trends and to develop an explanatory model. The Nordic Cancer Registries and the American Cancer Society provided age-specific incidence data. Birth cohorts of melanoma incidence for men were plotted against calendar year and age. A theory and a corresponding mathematical model were developed to explain the time trends in all cohorts, as well as the reported age-specific incidence and age-standardized incidence over time. A statistical distribution of time to sickness fitted all the post-1957 data. Earlier studies have indicated that body-resonant frequency modulation broadcasting radiation from 1955 onwards may affect melanoma incidence. The proposed model may shed light on the melanoma epidemic and may be useful in predicting future melanoma trends based on known birth cohort data and possible effects from policy changes with regard to population exposure to electromagnetic radiation.