The biomass yield, YX/S, and the specific growth rate, μ, of the ethanol-utilising yeast Candida valida was studied over a wide range of concentrations of two substrates, ethanol and zinc. The experimental results suggested that the cell maintenance rate, mS, was affected by each. Ethanol at high concentrations exerted substrate inhibition on the culture growth, which was manifested as a decrease of ethanol consumption rate and an increase of mS. A sharp increase of mS was observed at very low and high zinc concentrations, which might be a result of energy expenditure on zinc transport. The dependencies of biomass yield on specific growth rate during the variation of ethanol and zinc concentrations were two-branched, that for ethanol having the shape of a loop. A mathematical model of the cultures has been developed which is in good agreement with the experimental data.