Morphometric and quantitative analyses were carried out on the myenteric neurons of the duodenum, to study possible alterations resulting from a supply of low-protein level chow to adult Wistar rats. The animals were divided in two groups: nourished (N) fed with ration containing 22% protein for 210 days and the undernourished (D) fed with ration containing 8% protein from the 90th day of age on and during the next 120 days. Whole-mounts were stainedby the method of Giemsa and the histochemical reaction of NADH-diaphorase enzyme, to estimate the neuronal population, which revealed a greater neuronal density in undernourished rats, regardless of the technique employed. The morphometric studies of the cell body profiles of 500 neurons of each group indicated a reduction on the cell body size and an increase on the proportion of small neurons on the rats subjected to the hypoproteic chow