471 industrial employees from 27 occupations in four industries were surveyed to evaluate the role of occupational hand activity as a risk factor for slowing of sensory conduction of the median nerve at the carpal tunnel. After age-adjusting the latency values, slowing of the sensory fibres of the median nerve was found in 39% of the subjects and in 26% of the hands. No consistent association was found between the type and the level of occupational hand activity and the prevalence or the severity of slowing. In addition, the prevalence of bilateral slowing of conduction of the median nerve was not associated with bimanual occupational hand activity, and the length of employment of the subjects in the current industry did not influence the occurrence of impaired sensory conduction of the median nerve at the carpal tunnel.