This study was conducted to examine the usefulness of some of the commonly used biological parameters for monitoring of workers exposed to lead stearate. Forty-two lead stearate workers from a lead stabilizer factory and 26 workers exposed to inorganic lead compounds were involved in this study. Although the workers had similar blood lead values (PbB), subjects exposed to lead stearate were found to have a significantly higher concentration of lead in plasma (PbP), 1.0 +/- 0.57 micrograms dl-1) than workers exposed to inorganic lead compounds (0.42 +/- 0.3). The ratio of PbP to PbB was ca. 2.5 times higher for lead stearate workers (0.38) than the inorganic lead workers (0.15). These data suggest that the different chemical properties of lead stearate may result in different distributional patterns of the metal in different blood components. On the other hand, the activity of delta-aminolevulinic acid dehydratase (ALAD), an enzyme highly sensitive to lead, was not so much depressed among the lead stearate workers as that of workers handling inorganic lead. A poor correlation was also observed between PbB and ALAD activity of the stearate workers. These findings indicate that PbB and ALAD are not good biological indicators for evaluating the toxicological effect of lead stearate exposure.