Abstract: Melatonin is a bioactive compound that is present in wine because it is contained in vinification grapes and synthesized by yeast during alcoholic fermentation. The purpose of this study was to determine the capacity of various Saccharomyces strains to form melatonin during its growth and alcoholic fermentation. A selection of yeasts including six S. cerevisiae (Lalvin CLOS, Lalvin ICV-D254, Enoferm QA23 Viniferm ARM, Viniferm RVA, and Viniferm TTA), one S. uvarum (Lalvin S6U) and one S. cerevisiae var. bayanus (Uvaferm BC) were tested to determine whether they produce melatonin in yeast extract peptose dextrose and synthetic must media in a variety of conditions. Two S. cerevisiae strains (ARM, and QA23), the S. uvarum and the S. cerevisiae var. bayanus, synthesized melatonin. The conditions in which they did so, however, were different: the QA23 strain produced melatonin best in a medium with a low concentration of reducing sugars and Lalvin S6U and Uvaferm BC required a synthetic must under fermentation conditions. Melatonin synthesis largely depended on the growth phase of the yeasts and the concentration of tryptophan, reducing sugars and the growth medium. These results indicate that melatonin may have a role as a yeast growth signal molecule.