Inorganic lead is one of the most common sources of exposure in industry worldwide. To examine potential neuropsychiatric effects of occupational lead exposure, the authors conducted an epidemiologic study designed to mitigate the methodological difficulties. This chapter addresses three fundamental questions: Is the psychosocial and neuropsycho-logical functioning of lead workers significantly poorer than that of controls? Among lead workers, do higher levels of exposure result in impairments in neuropsychiatric functioning? Is there a synergistic effect of lead exposure and occupational stress on psychosocial functioning? The study found that exposed workers did not differ on most variables from non-exposed controls, nor were measures of prior and current lead exposure related to neuropsychological test scores. Lead exposure was somewhat related to one psychosocial parameter, namely, conflict in interpersonal relationships. The same pattern of results was obtained for a subsample of older workers who had been exposed to lead for a prolonged period of time.