Nitrous oxide flux and nitrogen turnover were measured in three types of Amazonian forest ecosystems within Reserva Florestal Ducke near Manaus, Brazil. Nitrogen mineralization and nitrate production measured during 10-day laboratory incubations were 3--4 times higher in clay soils associated with ''terra firme'' forests on ridge-top and slope positions than in ''campinarana'' forests on bottomland sand soils. In contrast, nitrous oxide fluxes did not differ significantly among sites, but were highly variable in space and time. The observed frequency distribution of flux was positively skewed, with a mean over all sites and all sampling times of 1.3 ng N2O-N cm-2 h-1. Overall, our flux estimates were comparable to or greater than those of temperate forests, but less than other reported for Amazonian. Results from a field fertilization experiment suggest that most nitrous oxide flux was associated with denitrification of soil nitrate. ¿ American Geophysical Union 1988