Blood lead level, urinary delta-aminolevulinic acid level, blood pressure, age, time of exposure, BMI were measured in zinc and lead foundry workers (n = 249) occupationally exposed to lead. Arterial hypertension was defined as the blood pressure over 140/90 and/or early diagnosed hypertension. Logistic regression analysis and correlation show that there is a relationship between ALA concentration and arterial hypertension (R = 0.12, p < 0.05). Workers were divided into a study group (ALA > or = 4 mg/l) and a control group (ALA < 4 mg/l). Both groups did not differ in age (mean 44.0 years in study group vs 45.3 in control group), time of exposure to lead (mean 21.1 years vs 21.7 years) and BMI (26.5 kg/m2 vs 26.7 kg/m2). Blood lead level was statistically significantly higher in the study group (23.5 micrograms/dl vs 16.8 micrograms/dl, p < 0.001) as well as urinary delta-aminolevulinic acid level (5.35 mg/l vs 2.79 mg/l < 0.001). In the study group there was a two fold increase in higher blood pressure in comparison with control group (OR = 1.90; 95% CI: 1.09-3.32). Exposure to lead even in small doses may increase arterial blood pressure and it seems to be associated with prooxidant effects of delta-aminolevulinic acid.