Since lead impairs in vitro the functions of macrophagic cells, we have studied the chemotactic activity of polymorphonuclear leukocytes (PMNs) obtained from lead acid battery workers who were removed from exposure one month before, because they had an abnormal lead absorption. Controls were 18 age matched subjects without any history of occupational lead exposure. Both lead acid battery workers and controls had no alterations of the blood haematological and metabolic parameters. Chemotaxis was carried on in Boyden chambers using zymosan activated serum as chemotactic stimulus. The chemotactic indexes are 56.4 +/- 8.7 in acid battery workers and 75.6 +/- in controls. The difference, which is statistically significant, shows that lead workers have an impairment of PMNs chemotactic activity.