The outline data concerning the 1127 abortions identified in 1110 Belfast resident women in 1957 are set out in Table 1. Summary Data are presented of 1110 women who had 1127 post 4‐week abortions which occurred in Belfast in 1957. These are believed to represent a high proportion of all such abortions which occurred in the city, but the frequency of 11.8 per 1000 pregnancies must be minimal. It is suggested that the true figure lies between this figure and 16 %. There is no evidence to suggest that more than a small fraction of abortions, say 1 %, are criminally induced. Data are also presented relating to 983 women who had 1002 consecutively admitted abortions in two hospitals (X and Y). This series was studied in more detail as more complete data were available. Aetiological factors are discussed.