This paper lists plant species collected and identified in the Nouabale-Ndoki Forest in northern Congo in the period from 1988 to 1992. It describes also the vegetation types and parts observed of plant foods eaten by gorillas and chimpanzees. The plant species composition led to grouping three vegetation types in the forest: mixed species forest, swamp forest, and monodominant forest of Gilbertiodendron dewevrei. Another two vegetation types, secondary forest and riverine forest, exist in the outer fringes of the study site. Collected plants contained 417 species (278 genera, 86 families), of which 400 were totally identified. Seven plant species were added to the flora of Congo.