The performance of fermentation processes is greatly influenced by the size and quality of inoculum. In experiments using yeast cells, all the cultures inoculated at different phases of growth of preculture reached similar amounts of maximum dry cell weight 8.92-9.38 g/L, and similar maximum specific growth rates, 0.169 +/- 0.01 h(-1), but had different lag phases. The inoculum size affected the cell growth rate, the maximum cell and ethanol concentrations. Data related to maximum total biomass showed an optimum size of 10% for inoculum for both free and immobilised cells. In terms of maximum ethanol productivities, the optimum inoculum size for free cells was 1% and for immobilised cells 20%, yielding 0.37 g ethanol/h-g cells and 0.32 g ethanol/h-g cells respectively.