The sexual habits in women aged 20-39 years chosen at random were investigated. A total of 513 women from Copenhagen participated while there were 586 women from Nykøbing Falster and 661 women from Nuuk (Godthåb) in Greenland. The women from Copenhagen replied to a questionnaire investigation while women from the other two regions were interviewed personally. The age of commencement of sexual activity was considerably lower in Godthåb in women of all age groups than in Copenhagen and Nykøbing Falster e.g. the prevalence of women with age on commencement of sexual activity less than or equal to 16 years was 70-80% in Godthåb while the corresponding figures for Copenhagen were 50-60% and for Nykøbing Falster 30-58%. Comparison with previous investigations revealed that the average age at the first coitus showed a tendency to decrease in all three regions during the past 20-30 years. The difference in the age at the first coitus between a provincial town (Nykøbing Falster) and a city (Copenhagen) was present only in the case of women in the oldest age group (35-39 years) and a geographical levelling appears to have occurred in the younger age groups (20-24 years) concerning the age at commencement of sexual activity. Women in Greenland had significantly more partners than women in the two South Danish regions. In Godthåb, the prevalence of women with greater than or equal to 40 partners was thus 22.4% while the prevalences in Copenhagen and Nykøbing Falster were 3.5% and 0.3%, respectively. The prevalences of women with 0-1 partners were 1.7%, 10.7% and 20.4%, respectively in Godthåb, Copenhagen and Nykøbing Falster.