[1] Stable carbon isotope ratios of methyl chloride (CH 3 Cl) were measured in foliar emissions from 14 species of tropical plants growing in a glasshouse. The isotopic ratio of CH 3 Cl (arithmetic mean: À83.2 ± 15.2%) ranged from À56% to À114%; that from dipterocarp trees (À87.4 ± 12.3%) was on average more depleted in 13 C than that from tree ferns (À61.9 ± 9.7%). The isotopic ratio was lower than that of CH 3 Cl produced by other known sources (e.g., biomass burning and salt marshes), with the exception of that by dead leaves. Using the distinctive isotope ratio of CH 3 Cl emitted from tropical plants together with previously reported isotopic data of CH 3 Cl sources and sinks to an isotopic mass balance calculation, global CH 3 Cl emission by tropical plants was estimated to be approximately 1500 -3000 Gg yr À1 with uncertainties of 30-60%, which could account for 30 -50% of the global emission. Citation: Saito, T., and Y. Yokouchi (2008), Stable carbon isotope ratio of methyl chloride emitted from glasshouse-grown tropical plants and its implication for the global methyl chloride budget, Geophys. Res. Lett., 35, L08807,