Leaf oil was isolated from two commercial samples of cilantro (Coriandrum sativum L.) and from growth-chamber-grown plants at five different stages of growth. The oils were analyzed by GC/MS. They were found to be composed mainly of C10−C16 aldehydes. (E)-2-Alkenals predominated. Substantial quantitative differences were observed between the two cilantro samples and in the leaf oils isolated at different growth stages. The data indicate that cilantro oil may exhibit significant variation in composition due to ontogenic factors. The data also suggest a possible link among growth stage, oil composition, and consumer preference. Keywords: Cilantro; Coriandrum sativuum; essential oil; ontogeny