This survey of occupationally acquired infections in clinical laboratory workers was made by questionnaires to 306 hospitals in which 698 doctors and 8654 technicians worked. There were 177 probable infections during the previous decade (1979-88). In both doctors and technicians annual incidence rate of infection was 0.2% on an average. These included 77 cases of tuberculosis, 59 cases of HBV hepatitis, 24 cases of non-A, non-B hepatitis, 6 cases of rubella, 5 cases of HAV hepatitis, 2 cases of mycoplasmal pneumonia, one case of campylobacter enteritis, one case of paratyphus, one case of salmonellosis and one case of chicken pox. There were no fatal cases. In the recent two years the occurrence of HBV hepatitis among the clinical laboratory workers apparently has decreased, but tuberculosis and non-A, non-B hepatitis occurred unchangedly. Tuberculosis occurred frequently among the staff of the pathology laboratory (40 cases) and in bacteriology (25 cases), but rarely in biochemistry (3 cases) and in hematology (one case). On the other hand, HBV hepatitis occurred frequently among the staff of the biochemistry laboratory (33 cases) and in hematology (11 cases), but rarely in bacteriology (one case). These differences showed the existence of occupational exposure, but only 20% of these cases were due to recognized accidents. According to these results infection control practices for diminishing laboratory-associated infection must be performed.