This is an ethnobotanical study of Atlantic Forest coastal communities located at Sepetiba Bay, Rio de Janeiro State, Brazil. Atlantic Forest remnants are top priority conservation areas, and include native communities that depend on fish and small-scale agriculture. We conducted fieldwork in the community of Calhaus (Jaguanum Island) from 1989 to 1991, and interviewed adults on their use of plants. We examined the diversity of medicinal plants used among communities of different islands and found results similar to previous research at Gamboa (Itacuruçá Island); communities living in smaller islands and on islands further from the coast use a lower diversity of plants. Also, older islanders show a deeper knowledge of medicinal plants than younger islanders.252353360Begossi, A., Sepetiba bay project: An ecological approach to fishing communities (1991) Human Ecology Bulletin, pp. 4-7. , Spring/SummerBegossi, A., The use of optimal foraging theory in the understanding of fishing strategies: A case from Sepetiba Bay (Rio de Janeiro State, Brazil) (1992) Human Ecology, 20 (4), pp. 463-475Begossi, A., Fishing spots and sea tenure: Incipient forms of management in the Atlantic Forest coast (1995) Human Ecology, 23 (3), pp. 387-406Begossi, A., The use of ecological methods in ethnobotany: Diversity indices (1996) Economic Botany, 50 (3), pp. 280-289Begossi, A., The fishers and buyers from Búzios Island (Brazil): Kin ties and production (1996) Ciência e Cultura, 48 (3), pp. 142-147Begossi, A., Leitão-Filho, H.F., Richerson, P.J., Plant uses at Búzios Island (1993) Journal of Ethnobiology, 13 (2), pp. 233-256Figueiredo, G.M., Leitáo-Filho, H.F., Begossi, A., Ethnobotany of Atlantic Forest coastal communities: Diversity of plants uses in Gamboa (Itacurucá island, Brazil) (1993) Human Ecology, 21 (4), pp. 419-430MacArthur, R.H., Wilson, E.O., (1967) The Theory of Island Biogeograpny, , Princeton: Princeton University PressMagurran, A., (1988) Ecological Diversity and Its Measurement, , Princeton: Princeton University PressQueiroz, M.S., Curandeiros do mato, curandeiros da cidade e médicos: Um estudo antropológico dos especialistas em tratamentos de doenças na região de Iguape (1980) Ciência e Cultura, 32 (1), pp. 31-47Zar, J.H., (1984) Biostatistical Analysis (2nd Ed.), , Englewood Cliffs, NJ: Prentice-Hall