Information obtained in a number of experimental studies conducted over the last forty years on the effects of lead on blood pressure is reviewed. Differences in animal species, age at beginning of exposure, level of lead exposure, indices of lead burden, and blood pressure effects of each study are reported. In several of the high-dose experiments, hypertension was observed, but nephrotoxicity of lead may have contributed to its development. Moreover, in other high-dose experiments, no hypertension was observed and in at least one, the evidence suggested that lead could reduce an elevated blood pressure. In contrast, the lower-dose experiments consistently demonstrated a hypertensive effect. Overall, the data suggest a biphasic dose response.