The Congo Basin lowland forest represents one of the largest tropical forest blocks in the world but its liana assemblage has never been characterized. We evaluate liana floristics diversity and structure in the Ituri Forest and determine the effects of forest structure and edaphic variation on liana species composition.\n\nMethods – Two permanent 10-ha plots (200 × 500 m) 500 m apart were established in mixed forest. All liana individuals = 2 cm dbh were identified measured mapped and marked. For 20 × 20 m subplots we distinguished terra firme and swamp and we estimated canopy openness.\n\nKey results – The combined 20-ha area contains 15008 lianas (dbh = 2 cm) representing 195 species 83 genera and 34 families. Per hectare species number averaged 64 mean basal area was 0.71 m2 and mean Fisher\\\s alpha Shannon index and Simpson diversity index values were 17.9 3.1 and 11.4 respectively. Ten dominant plant families represented 69% of total species richness 92% of liana abundance and 92% of basal area while ten dominant species accounted for 63% of abundance and 59% of basal area. A single species Manniophyton fulvum dominated the liana community (22% of all individuals). Forty-one species (21%) had one individual only. Twiners zoochorous light-demanding and meso- or microphyllous species dominated. Liana abundance increased with abundance of medium-sized and large trees but was surprisingly independent of small-tree abundance. Canopy openness habitat type and tree size were the most important factors influencing abundance and distribution of liana individuals.\n\nConclusions – The Ituri liana assemblage stands out by showing an extreme one-species dominance. Species floristic composition is however generally similar to that in other tropical African forests.