γ-Decalactone is a peachy aroma compound resulting from the peroxisomal β-oxidation of ricinoleic acid by yeasts. The expression levels of acyl-CoA oxidase (gene deletion) and 3-ketoacyl-CoA thiolase activities (gene amplification on replicative plasmids) were modified in the yeast Yarrowia lipolytica. The effects of these modifications on β-oxidation were measured. Overexpression of thiolase activity did not have any effect on the overall β-oxidation activity. The disruption of one of the acyl-CoA oxidase genes resulted in an enhanced activity. The enhancement led to an increase of overall β-oxidation activity but reduced the γ-decalactone production rates. This seemed to indicate a non-rate-limiting role for β-oxidation in the biotransformation of ricinoleic acid to γ-decalactone by the yeast Yarrowia lipolytica. All strains produced and then consumed γ-decalactone. We checked the ability of the different strains to consume γ-decalactone in a medium containing the lactone as sole carbon source. The consumption of the strain overexpressing acyl-CoA oxidase activity was higher than that of the wild-type strain. We␣concluded that peroxisomal β-oxidation is certainly involved in γ-decalactone catabolism by the yeast Y.␣lipolytica. The observed production rates probably depend on an equilibrium between production and consumption of the lactone.