The Mini-Horto Sylvio Potsch is situated at Colegio Pedro II in Sao Cristovao. Rio dc Janeiro, and is an area built on several landings on a natural elevation, used for aesthetical, recreational and teaching purposes and containing six tanks of differents levels. They are fed by a big water tank and are maintained full during all the year. The characteristic vegetation of the tanks consists of mainly: Elodea canadensis and E. densa (Hydrocharitacea), Eichhornia crassipes (Pontederiaceae), Nymphaea sp. (Nymphaeaceae) and Utricularia sp. (Utriculariaceae). We report now the results of a study of the odonate fauna of these tanks, as a first step toward the understanding of the adaptation of dragonflies to the urban environment of the city of Rio de Janeiro. During the months of September to December 1985 and January to April 1986 periodical visits were made to the study area in order to collect larvae and imagines. The imagines were collected near the tanks except for Triacanthagyna septima Sel. which was collected inside the building of Colegio Pedro II. Most of the larvae were collected on the roots of Aguape ( Eichhornia crassipes) and in the branches of Elodeas. They were reared in small styrofoam boxes yielding 48 emergencies. Identification was always based on adult characters.