An experimental evaluation of artificial reefs was carried out on the coast north of Rio de Janeiro, a low-relief bottom area. The reef complex (1500 m 2 ) consisted of two sets (concrete and tire), each comprising 16 modules. Trammel nets were used in monthly samplings of the reef site and a control area. During 2 years of monitoring, 51 fish species were recorded in both areas, of which 24% and 11%, respectively, were found exclusively at the reef and in the control area. The most abundant families were Carcharhinidae, Carangidae, and Triakidae. Based on c.p.u.e. in numbers and weights, density and biomass appear to be higher at the reef site than in the control area. At the reef, species richness and diversity were generally higher during the second year, which may reflect the degree of fouling. Visual observations revealed higher fish diversity on concrete experimental structures than on tire modules. The effectiveness of the reef in creating a complex habitat for the fish community is shown by the dominance of the shark (Rhizoprionodon lalandei), a predator of small teleosts commonly found on the reef structures.