Carotenoid production by Rhodotorula aurantiaca K-505 was optimized in shake-flask cultures using a central composite design. Quadratic polynomial models were used to correlate the relationships between six fermentation factors (pH, temperature, and the concentrations of glucose, yeast extract, peptone extract, and ammonium sulfate) and three response variables (cell mass yield, carotenoid content, and carotenoid production). Different optimum culture conditions were predicted by the models for maximizing the three response variables, indicating that there is no direct correlation between cell growth and carotenoid production. The maximum carotenoid production of 4.9 mg/L predicted by the relevant model under optimum culture conditions agreed well with the experimentally measured value of 5.3 mg/L under the same culture conditions.