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-scall 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 (Itacuruca 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.252353360