Stable carbon isotope analysis of tree rings has become a widely used proxy in environmental and palaeoclimatological studies. In those studies, a-cellulose has often been the preferred material because of its singular composition and its immobility in wood. However, cellulose extraction is a time-consuming procedure and since the development of on-line isotope ratio mass spectrometers has become the time-limiting step in the isotopic analysis of wood samples for dendrochemical purposes. In this study we evaluate the necessity of cellulose extraction for isotopic analysis of tree rings in a tropical mangrove tree, Rhizophora mucronata Lam. Comparison between the d 13 C of extracted a-cellulose and bulk wood material revealed a highly significant linear relationship (d 13 C bulk wood = 0.92 (F 0.08) * d 13 C a-cellulose À 2.91 (F 2.04); p b 0.001) for a-cellulose values between À24x and À27x. However a-cellulose was on average 0.97 F 0.03x enriched in 13 C as compared to bulk wood. The slope of the regression was not significantly different from one (p b 0.05). Furthermore, no significant difference was found between either the d 13 C bulk wood À d 13 C a-cellulose slopes for earlywood and latewood or between the slopes for samples from trees growing in contrasting environmental conditions. These results indicate that bulk wood can be used instead of a-cellulose when measuring stable carbon isotopes in the sapwood of R. mucronata in the context of a dendrochronological investigation. D 2005 Elsevier B.V. All rights reserved.