The relationship between blood pressure (BP) and blood lead concentration (PbB) was examined in 51 bus drivers who were treated for hypertension. These drivers were a subset of a representative sample (N = 342) of the driver population (N = approximately 2,000), and were not selected for hypertension or lead exposure. Blood lead concentrations ranged from 2-24 micrograms/dl (median: 6.9 micrograms/ld). There were 33 subjects treated primarily with diuretics, and 18 subjects were treated with beta blockers. Adjusted regression coefficients relating systolic BP with PbB were -6.4 +/- 11.4 and 4.5 +/- 12.9 mmHg/In(micrograms/dl) in each group, respectively, but were not statistically significant. The adjusted coefficients for diastolic BP were 1.12 +/- 3.89 and 14.3 +/- 5.69 mmHg/In(micrograms/dl) (p = 0.036), respectively. The latter relationship represents an average increment of 12 mmHg in diastolic BP over the range of observed PbBs (2.0 to 11.4 micrograms/dl) in subjects treated with beta blockers. Thus, beta blocker therapy may be less effective in reducing diastolic pressure in individuals with higher PbBs and suggests an action of lead at PbBs below current standards.