A representative population sample comprising 1,462 women was studied in Gothenburg, Sweden in 1968-69, and a third follow-up study was carried out in 1980-81. The participation rates in the baseline study and during the follow-up studies were high. In 1980-81 women in two new age strata, aged 26 and 38, were added. Women who had moved to or from Gothenburg during the study period were not found to differ from those who were living in Gothenburg during the total study period, while there were a few differences of statistical significance between refusers and participants in 1980-81. The mortality among initial refusers was about doubled compared to that of those who participated in the baseline study.