Lead is considered one of the major environmental toxicants that causes hematological, neurological, and gastrointestinal dysfunction. In this study, the authors examined the relationship between lead and lipid peroxidation, lead and Na+-K+ ATPase activity, and lead and Ca+2 ATPase activity in blood of workers. The working group consisted of 30 male workers occupationally exposed to lead at least for 10 years. The control group consisted of 20 healthy male individuals not involved with job-related lead exposures. Blood lead content of the control group and the working group were 10.0 +/- 1.8 mug/dl and 317.3 +/- 47.6 mug/dl, respectively. Malondialdehyde ( MDA) value of the working group (0.57 +/- 0.30 nmol MDA/ml) was significantly greater than MDA value of the control group (0.17 +/- 0.02 nmol MDA/ml). In the working group, both Na+-K+ ATPase activity (105.0 +/- 47.0 nmol Pi.mg protein(-1).h(-1)) and Ca+2 ATPase activity (58.0 +/- 40.0 nmol Pi.mg protein(-1).h(-1)) were lower compared with the corresponding values of Na+-K+ ATPase activity (247.0 +/- 41.0 nmol Pi.mg protein(-1).h(-1)) and Ca+2 ATPase activity (230.0 +/- 41.0 nmol Pi.mg protein(-1).h(-1)) of normal controls. The results show that lead exposure causes inhibition of Na+-K+ ATPase and Ca+2 ATPase activities and also results in increased lipid peroxidation.