La Selva Biological Station is a lowland tropical rainforest site in Costa Rica. It is owned and operated by the Organization for Tropical Studies, a consortium of over 30 US and Latin American universities, and plays a key role in the ecological training and research of the scientists of the Western hemisphere. Since the initiation of improved laboratory facilities in 1983 and the completion of expanded living accommodations in 1986, La Selva has moved to a higher plateau of research sophistication and expertise that is involving a far wider spectrum of biological scientists than ever before. Current collaborative efforts between physiological ecologists, population biologists, community ecologists, ecosystem researchers and systematists have resulted in exciting synergistic approaches that promise to achieve a new level of understanding about the tropical rainforest ecosystem. Collaborative research activities at La Selva have also inevitably led to an expanded need for analytical facilities to address fundamental biological questions about the tropical rainforest. This project will address part of that need by providing funds for a 4000-square-foot, air-conditioned research laboratory to permit plant chemistry and large-scale soil analyses. Because of La Selva's ties to an increasingly larger proportion of the tropical research community, this facility will benefit users from an exceptionally broad geographic and disciplinary spectrum.