A model of toluene level in blood following subcutaneous injection of toluene mixed with polyoxyethylated vegetable oil vehicle was developed. The purpose was to provide a means of predicting dose received, for subsequent toxicologic studies for any time and dose comuination. The pharmacokinetics were of secondary interest. Using data from 111 rats, a 4-parameter equation was devised to predict the time course of toluene blood level from 20-480 min., for dose levels of 500-1000 mg/kg. Blood concentrations rose at a rate which was independent of dose level. Maximum blood levels were uniquely determined by dose level. Blood levels fell at different rates, depending upon dose level. Injection exposure, when compared to inhalation, has the advantages of (a) low expense (b) low equipment requirements and (c) simplicity. The disadvantage is, for some experiments, poor temporal simulation of the normal route administration, inhalation.