As the authors purpose was to study the effect of shale resins on worker health, an appropriate group was selected and the tests conducted on persons for whom the main occupational agent was shale resin. All workers were examined by an occupational pathologist-therapist and a neuropathologist. Study data were entered on specially devised punch cards. In order to investigate the condition of the autonomic nervous system the authors determined the sensitivity of the skin to ultraviolet rays, sweat production and skin temperature of the digits, hands and feet. Besides clinical analysis of the blood, the authors also determined the content of free and bound phenols, sulfates, glucuronic acids and coproporphyrin in urine.