Abstract Fruit of 39 peach and nectarine cultivars were harvested at commercial maturity from an orchard between June 5 and September 9 in 2010. Total soluble solids (TSS) concentration ranged from 8.90% to 19.97%, titratable acidity (TA) concentration ranged from 0.20% to 1.12%, and TSS/TA ratio ranged from 9.36 to 92.80 in the tested pulp samples of 39 cultivars. Pulp volatiles of 39 cultivars at harvest were evaluated by a FOX 4000 electronic nose (e-nose) equipped with 18 metallic oxide sensors, which 13 sensors were positive and five sensors were negative in intensity values. Based on e-nose measurements of pulp volatiles of 39 cultivars at harvest, cultivars harvested in June, July, and both August and September could be differentiated, cultivars of low TSS concentration ( 16%), and cultivars of low TSS/TA ratio ( 45) in the discriminant factor analysis (DFA) plot of 39 cultivars. 117 samples of three replicates for each cultivar were separated into three individual groups according to the classifications of harvest season, TSS concentration and TSS/TA ratio, respectively. Clearer separations were reached in these DFA plots of separated 117 samples than that of 39 cultivars based on pulp volatiles at harvest measured by the e-nose.