Sixteen lactating Girgentana goats were used to evaluate the effect of polymorphism at αs1-casein locus on milk fatty acids composition. Animals, homogeneous for milk production, days of lactation and body weight, were divided into two groups: eight homozygous for strong allele (AA group) and eight homozygous for weak allele (FF group). The experimental diet, identical for the two groups, consisted of alfalfa hay (1.5 kg), whole barley, whole maize, pelleted sunflower and whole faba bean (0.5 kg each). In spite of identical selected diets, also in terms of fatty acids, milk fatty acid composition resulted different between the two groups. In particular, except for C8:0, short and medium chain fatty acids and odd chain fatty acids resulted in higher percentage in the AA group. Taking in account that the difference reported in our experiment concerns above all de novo synthesized fatty acids, our results seem to confirm the hypothesis that polymorphism at αs1-casein locus can influence milk fatty acid composition in goats.