The vegetation composition and structure of “pristine” primary lowland rainforest in Waisoi, south Viti Levu, Fiji were assessed quantitatively by recording all trees with a diameter at breast height > 1 cm within sample plots covering the topographic range of the Waisoi area. The tree flora comprised 78 recognizable taxa, 68 of which were recorded to species. Of these 68 species, 61% were endemic. Four forest types were evaluated; “River Flat,” “Slope,” “Ridge,” and “Quasi-montane.” Differences in stem density, species richness, and diversity were observed across the forest types. The River Flat and Quasi-montane forest types were distinct from each other and from Slope and Ridge forests. Canopy structure was characterized for each of these forest types and illustrated with profile diagrams.