Decreased tissue oxygenation resulting from iron deficiency anaemia produces generalized weakness and fatigue. The precise physiological mechanism underlying this weakness is unknown and studies in this regard have been scarce. One possible underlying mechanism has been suggested to be reduction of spinal motoneuron excitability. F waves are low amplitude motor responses to nerve stimulation, produced by antidromic activation of the peripheral motor fibers, resulting in recurrent discharge of motoneurons. F waves have been established as an efficient tool to assess spinal motoneuron excitability. 15 patients of iron deficiency anaemia using inclusion criteria of hemoglobin level < 9 g/dL and serum ferritin < 15 microg/L were studied. 8 controls with hemoglobin levels > 12 g/ dL were also included. Bilateral median and common peroneal F wave studies were performed. F wave mean latency, chronodispersion, persistence and mean amplitude were studied. They were within the normal range and no significant differences between the patients and the controls were found. We conclude that spinal motoneuron excitability is not reduced in iron deficiency anaemia. A decreased tissue oxygenation leading to a change in the brain neurotransmitters may have a role to play.