In beef suckler cows, the prolonged interval from calving to first ovulation (post-partum interval, PPI) is due to failure of ovulation of dominant follicles. It appears that a combination of poor body condition, maternal calf-bond and suckling act to suppress the LH pulse frequency necessary for ovulation. A combination of calf isolation and once-a-day suckling can significantly shorten the PPI, but the first ovulation generally occurs without overt oestrus and the subsequent cycle is short (8 to 11 days) due to lack of progesterone priming. The aim of this study was to examine the effects of progesterone or progesterone and oestradiol in conjunction with calf isolation on the interval to first ovulation, incidence of overt oestrus at first ovulation and length of the subsequent interovulatory interval.