To evaluate diagnostic and aetiological clues for diffuse cerebral atrophy, the statistical correlations between 35 pneumoencephalographic and 97 clinical variables in 268 patients were analysed. Each case of diffuce cerebral atrophy was originally of unknown cause, and all had pneumoencephalography. Ventricular diffuse atrophy correlated positively with psychic and co-ordinative impairment and dysarthria, and cortical diffuse cerebral atrophy with psychic impairment (P smaller than 0.01 to 0.001). There was a close correlation (P smaller than 0.001) of cortical diffuse cerebral atrophy with use of vibrating tools at work. Psychic impairment combined with co-ordinative dysfunction and dysarthria is an unspecific syndrome, but should make one think of diffuse cerebral atrophy, Arteriosclerosis, abuse of alcohol, and vibrating tools at work appear to have aetiological significance for some types of diffuse cerebral atrophy. Thus the number of patients with idiopathic diffuse cerebral atrophy may rapidly decline.