As Phaffia rhodozyma is a Crabtree positive yeast, its cell yield and pigment production are reduced at high sugar concentrations. A method for maintaining low growth medium sugar concentrations is fed-batch culture. Using a mass balance approach and Monod growth kinetics a model is presented which describes the fed-batch culture of Phaffia rhodozyma and enables the calculation of a feed regime to obtain the maximum yield of cells and pigment. Although developed on a glucose medium, the model was also applied successfully to a molasses-based medium.