The influence of culture media composition on carotenoid production by Phaffia rhodozyma strain NRRL, Y-17268 has been studied. Typical fermentation media containing xylose as a carbon source were supplemented with inorganic nitrogen sources (ammonium phosphate, ammonium sulphate, ammonium nitrate or potassium nitrate) in concentrations up to 5 g litre(-1). The presence of inorganic nitrogen sources at selected concentrationsimproved carotenoid production. Volumetric concentrations of 5 mg total carotenoids litre(-1) with 4.3 mg astaxanthin litre(-1) were achieved in media containing 0.2 g KNO3 litre(-1). In experiments carried out in xylose-containing media, the concentrations of yeast extract, malt extract and peptone were considered as operational variables for assessing their effects on carotenogenesis. The type and concentration of the inorganic component was fixed in the optimum value determined in the previous assays. The experimental results allowed the development of empirical models useful for optimization purposes. Under the best operational conditions, 5.8 mg carotenoids litre(-1) with 5.2 mg astaxanthin litre(-1) were obtained.