Using the 1987-88 California Activity Pattern (CAP) Survey, the report examines various microenvironmental aspects of personal exposure to environmental tobacco smoke (ETS) that were not explored in earlier reports. These topics include: (1) predictors of those individuals with the highest ETS exposures, (2) daily activities and locations associated with higher and lower amounts of ETS exposure, with special emphasis on the workplace, (3) ETS exposure for persons in those locations with exposure to other sources (for example, gasoline, gas stoves, or chemicals at the workplace). From a multivariate analysis, the report concludes: (1) education remains a major demographic predictor of potential ETS exposure among individuals; (2) time spent working was a major and consistent correlate of exposure to ETS, while drinking at bars/lounges and eating out at restaurants also were significant correlates of ETS exposure; (3) respondents who reported the presence of dust particles at work also reported significantly higher ETS exposure and were exposed to other potential pollutant sources as well. These analysis generally confirm the important role of workplace factors in the public's exposure to ETS.