At different developmental stages, citronella Java (Cymbopogon winterianusJowitt) leaves were analyzed for essential oil content and composition. Only immature leaves (up to 75% leaf expansion) were biogenetically active to synthesize and accumulate essential oil substantially. The relative percentage of geraniol and citronellol in the oil from immature leaf increased with increase in tissue age along the leaf blade, and was accompanied by a corresponding decrease in geranyl acetate and citronellyl acetate. During leaf ontogeny, the amount of citronellal, geraniol and citronellol in the essential oil increased with leaf expansion; whereas, the amount of geranyl acetate and citronellyl acetate decreased. As the leaf matured, a significant decrease in the essential oil, citronellal and geraniol contents was observed. The essential oil level showed a highly significant linear association with the citronellal and geraniol content; whereas, the geraniol content was positively correlated with citronellol and citronellal content. Oil content was also significantly associated with leaf dry weight and chlorophyll content. The results are consistent with geraniol to citronellol and citronellol to citronellal in vivo interconversions of the monoterpene constituents.