The outcome of pregnancies in the county of Sør-Trøndelag, in Norway, during the 27 months preceding and 21 months after the Chernobyl accident has been analysed on the basis of time of conception. The analysis showed a significant decrease in the number of conceptions during the three months immediately after the accident (April-June 1986). This finding can be interpreted to mean fewer "planned" conceptions. The Chernobyl accident did not seem to have had any impact on the proportion of conceptions ending as spontaneous abortions or ectopic pregnancies. There was a significant drop in the proportion of pregnancies ending as induced abortions during the year after the accident compared with the year before. However, due to some variation during this year it is difficult to draw any definite conclusions concerning the impact of the accident on induced abortions in this county. The proportion of pregnancies ending as births increased significantly during the year after the Chernobyl accident compared with the year before.