Lead is a toxin widely used in industry. Recently, medical investigation into lead exposure has turned to testing organ systems, such as the immune system, that historically were not associated with lead poisoning. We evaluated the effects of doses of 13, 130 or 1,300 ppm of lead on the adherence of mouse peritoneal cells, and particularly on macrophages. Cellular adherence was measured according to the De la Fuente technique. Adherence of macrophages showed significant changes in the 1,300 ppm group, revealing a reduction to 55% of the control group. The macrophage adherence index showed 91% sensitivity and 96% specificity. These results indicate a considerable reduction in the adherence of peritoneal macrophages following exposure to certain levels of lead.