We have examined the number of nerve cells present in the myenteric plexus of the human large intestine using a nonhistochemical method (Giemsa) in laminar preparations of the muscularis externa in two groups of subjects aged 20-35 and over 65 years. The collagen and elastic system related fibers in the myenteric ganglia were also qualitatively evaluated. The total number of neurons decreased in the old subjects by over 37%. The perikaryal area of most of the neurons in both the young and old subjects fell from 101 to 200 microns2. A ganglionic capsule was present and was thicker in the ganglia from the old subjects as were the septa within the ganglia. Both collagen and elastic system fibers were more numerous in the ganglia from the old subjects. We conclude that the decrease in neuron density with age is accompanied by an apparent increase in the fibrous components of the myenteric ganglia.