Data collected during 1958.60 on 4596 gestations of saddle horses (Groningen or Gelderland type), draft horses, Friesians and Shetland ponies are tabulated. The proportion of pregnancies lasting 330.340, 330-350 and 320-360 days was 41, 71 and 93% resp. Age of mare did not affect gestation length. Average gestation length in the 4 breed groups was 340, 339, 337 and 338 days resp.
