The state of our knowledge of the cellular events connecting the LH stimulus to ovulation with rupture has been reviewed. The evidence indicates, with varying degrees of certainty, that the follicular reaction to the LH-receptor complex has a minimum of two discrete steps: the stimulation of steroid synthesis by the LH, and the activation of an ovulatory enzyme by the steroid released. The sequence of events leading to steroid synthesis involves the activation of adenyl cyclase by the LH-receptor complex, perhaps through the local action of a prostaglandin, which results in increased tissue levels of cyclic AMP. Cyclic AMP then induces protein synthetic process essential to increased synthesis of progesterone. Thus, stimulation occurs between cholesterol and progesterone and is correlated with an increase in 3β-hydroxysteroid dehydrogenase activity. The progesterone stimulates protein synthetic activity, involving both transcription and translation, essential to the elaboration of an enzyme which weakens the collagen framework of the theca externa. Suggestions are offered for further studies to corroborate or refute these observations and to determine more precisely the nature, timing, and site of these cellular events.