From 1961-66 to 1973-78 in Uppsala county, Sweden the overall incidence rate of ectopic pregnancy rose from 0.31 per 100 notified pregnancies or 0.28 per 1 000 women 15-44 years of age, to 1.00 and 0.96, respectively. The impact of demographic changes on the increase in the overall incidence was studied. By using indirect age standardization it was found that 13% of the increase in the overall rate of ectopics per 1 000 women was attributable to a change in the age distribution of women in the fertile age-span.