Iron toxicity is the most common chemical stress in lowland rice systems in West Africa. The soluble iron accumulates in leaves and causes severe yield reductions, associated with leaf discoloration and poor growth. The relationship between leaf iron accumulation and two parameters relevant to carbon assimilation [specific leaf area (SLA) and chlorophyll content] show two differents comportments for a susceptible variety (Bouake 189) and a tolerant variety (CK4). Leaves of the two test varieties responded differently to iron toxicity. While older leaves generally contained more iron than young leaves, the concentrations were much higher in Bouake 189 than in CK4. The latter, tolerant variety, therefore, absorbed less iron or transported less to the leaves. Accumulation of iron in the leaves of Bouake 189 was associated with a significant increase of SLA, which is the leaf area produced with a given amount of dry weight. Consequently, iron-stressed leaves were thinner than non-stressed leaves. The tolerant check CK4 showed no such response. CK4 had a significantly higher leaf chlorophyll concentration than Bouake 189, indicating a higher photosynthetic potential. Observations on both SLA and chlorophyll content indicate that any given amount of iron present in the leaves reduced photosynthetic rates more strongly in Bouake 189 than in CK4. In summary, CK4 owes its superior performance under iron toxic conditions partly to avoidance (less iron accumulation in leaves) and tolerance (superior photosynthetic potential under iron toxic conditions).