The effect of different summary measures of worklife exposure on the estimation of risk is reported. Two matched case-referent studies associating sulfuric acid exposure and cancer from Baton Rouge and southern Ontario were used. Five summary exposure measures were converted to discrete levels of exposure through the selection of equivalent percentile points on each measure's respective percentage frequency distribution for logistic regression modeling purposes. The southern Ontario data set exhibited only minor differences across all five exposure measures. The Baton Rouge data set, however, produced different results, and the time-dependent measures appeared to underestimate risk. It is possible, therefore, to obtain different estimates of risk depending on the exposure measure selected. It is recommended that, in the absence of proved models for assessing exposure, a variety of summary measures be used to estimate risk. This approach would facilitate the comparison of findings across studies.