ABSTRACTThe effects of the inoculum ratio of Williopsis saturnus var. saturnus NCYC22 and Saccharomyces cerevisiae var. bayanus EC-1118 at 1:200 and 1:800 on the chemical and volatile compositions of grape wine were studied in sequential fermentation. The grape juice was first inoculated with Williopsis (W.) saturnus for 9 d; thereafter, Saccharomyces (S.) cerevisiae was inoculated to continue the fermentation until d 19. The cell population of W. saturnus disappeared by d 13, with S. cerevisiae dominating until the end of the fermentation in both inoculum ratios. The changes in yeast count, pH, total soluble solids, sugars, organic acids, and amino acids were similar between the two inoculum ratios. A range of volatile compounds was formed, including alcohols, esters, fatty acids, aldehydes, and terpenes. There were significant differences between both inoculum ratios for medium-chain fatty acids (C8, C10, and C12), ethyl esters of fatty acids of C6, C10, C12, and C14 as well as isoamyl octanoate, while other volatiles were statistically the same.