An important feature of reproduction in sheep and goats is its seasonality. In most feral breeds originating from mid and high latitudes, birth occurs over a very limited period in the spring. A Photoperiod is the main environmental factor responsible for the seasonality of reproduction in sheep and goats. Evidence for a role of melatonin in mediating photoperiodic information came from its ability to produce short-day effects in animals exposed to long days and to mimic the effects of photoperiod in Px or ganglioectomized sheep and goats. Photoperiodic changes and/or melatonin treatments are also able to entrain modifications in sheep and goat fleeces. In recent years, the interest in photoperiodic and melatonin treatments to control seasonality of reproduction in both sexes of sheep and goats has strongly increased for several reasons. Daily distribution of melatonin is a prerequisite to obtain the precocious onset of ovulatory activity.