Concentrations of progesterone in peripheral plasma of red deer hinds were basal ( < 1 ng/ml) during lactation/seasonal anoestrus, but increased abruptly at the onset of the breeding season. Lactating hinds (N = 19) started ovarian cycles 10 days later (P<0\m=.\01) and conceived 16 days later (P< 0\m=.\001) than did 13 weaned hinds. There was no evidence, from plasma progesterone values, of silent oestrus at the start of the season. Progestagen/PMSG treatment induced early ovulations in 8

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... rous hinds but fertility was low, only 2 conceiving and giving birth. Pregnant hinds (N = 42) had high plasma concentrations of progesterone (mean 3\p=n-\5 ng/ml) which declined just before parturition.