Summary All the cases of clinical hepatitis B reported in Sweden since 1969 have been studied. The 10-year period 1976–1985 has been analysed intensively. For comparative purposes, the study also includes the hepatitis cases reported in 1962 and 1967. Serum hepatitis first affected young adults aged 15–24 years at the beginning of the 1960s. Cyclical outbreaks of hepatitis B due to transmission among drug abusers have been recognised since 1969. The disease was first observed in urban areas but later in rural parts of Sweden also. After 1976, a year in which outbreaks arose in various parts of Sweden, the numbers of hepatitis B cases decreased. In 1969, more than 50% of the cases reported as serum hepatitis concerned drug abusers. During the period 1976–1985, the main risk factor was drug abuse for between 20 and 52 % of cases and sexual activity for between 8 and 28 % of cases. Since 1969, 2–3 % of cases annually have been related to blood-transfusion. In the last 5-year period, a total of 129 cases was reported among persons employed in the medical and dental fields. Of these, 59 had non-occupational exposure. During the same period, 33 patients reported contacts with infected persons, mostly household contacts. Seventy five persons had been travelling abroad.