Three groups of volatile compounds, i.e., alcohols, aldehydes and esters, were tested for their effects on arthrospore germination and mycelial growth of Geotrichum candidum citrus race, the causal agent of citrus sour rot. Alcohols (heptanol, octanol, nonanol, decanol, geraniol, citronellol) at a concentration of 1,0 μl/ml showed 60% or more inhibitory effects on both germination and mycelial growth of this pathogen, Among aldehydes tested, only citral had an inhibitory effect of more than 50%, while esters had no effect. The chain length of straight-chain (C6–C12) alcohols correlated with inhibitory effect, and nonanol (C9) was most active, Treatment with alcohols or citral prior to inoculation reduced colonization and maceration of lemon peel by this pathogen by 70% or more, Results suggested that alcohols or citral can probably be used to prevent the development of citrus sour rot.