The aim of this work was to study the formation of vinylphenolic pyroanthocyanin pigments by three strains of Saccharomyces cerevisiae and one strain each of Saccharomyces uvarum and Saccharomyces montuliensis during the fermentation of red grape (Vitis vinifera L. cv. Tempranillo) must containing additional hydroxycinnamic acids (caffeic acid, ferulic acid or p-coumaric acid, 50 mg/l). These pigments were identified and quantified by high pressure liquid chromatography-diode array detection, their structures confirmed by liquid chromatography/electrospray interface-mass spectrometry, and their mechanisms of formation proposed. Depending on the yeast strain employed, different quantities of these pigments were formed. These pigments affect the colour of the finished wine, sometimes greatly intensifying it.