The indigenous sheep breeds in Greece have a relatively short anoestrus. Some ewes begin to cycle before June but there is considerable variation, both between the within breeds, which may be associated with genotype or with environmental factors. Mating in spring or early summer, with or without synchronisation, is a common practice in order to take advantage of the climatic conditions and of the traditional marketing period for suckled lambs. In many cases the ewes are still being milked daily and are in low body condition. Conception rate is often low and the lambing period - in flocks of around 100 ewes - may extend over several months. Melatonin is known to advance the onset of oestrus in autumn breeding ewes but treatments initiated before June have given equivocal results.