Dichloromethane-methanol (1:1) extracts of ten species of alcyonacean soft corals were screened for post-coital interceptive effects on female rats, using oral administration, from day 1 to day 7 of pregnancy. Significant suppression of fertility was observed in the animals treated with the crude extracts of Sarcophyton ehrenbergi (250 mg/kg/day, P less than 0.05; 500 mg/kg/day, P less than 0.001), Sinularia crispa (500 mg/kg/day, P less than 0.05; 1000 mg/kg/day, P less than 0.001), Sinularia abrupta (1000 mg/kg/day, P less than 0.001), Sinularia spp--III (500 mg/kg/day, P less than 0.05). This antifertility effect appears to be due to interruption of embryonic events during implantation and/or pre-implantation periods.