the incidence of malignant melanoma (MM) has doubled during the past 25 years, with an incidence of 29.5 and 31.7 per 100 000 person-years in 2012 for men and women, respectively. Understanding the nature of this increase in incidence is important to optimize prevention, early diagnosis, and treatment of in situ and invasive melanoma in Denmark. OBJECTIVE To describe changes over time in the incidence and clinical and pathologic characteristics of in situ and invasive melanoma in Denmark from 1985 through 2012. DESIGN, SETTING, AND PARTICIPANTS We used the official national Danish Melanoma Group database to describe all eligible, prospectively registered cases of in situ and invasive