The results of this work demonstrate that a significant exposure to one of several lead compounds can be detected by the ALAD test without a concomitant rapid increase in blood lead concentration. Use of the ALAD test may effectively demonstrate the occurrence of excessive exposure at an earlier time than possible by the accepted blood or urine lead concentration measures. By comparing "early" and "steady state" values of PbB and ALAD, it was possible to derive an equation which can be used to determine an ultimate (steady state) value of PbB from an early (short-term) ALAD measurement. Re-examination of workplace atmospheres would be indicated by findings of depressed ALAD activity in the absence of elevated blood lead values. This could occur when sporadic lead exposures are occurring or upon initiation of a period of continuing elevated exposures. Thus, corrective action can be requested and taken prior to the point at which an excessive blood lead value would be found. Further studies of industrial groups are indicated to confirm the usefulness of the test for the purposes suggested.