The purpose of this study is to assess by age, race, ethnicity, and income the effects of air pollution control measures and population growth on human exposure to ozone in the South Coast Air Basin of California (SoCAB). A methodology to study human exposure to air pollutants from a socioeconomic perspective has been developed. Specifically, the Regional Human Exposure model (REHEX-II) has been applied to estimate historical (1980-1982) and recent (1990-1992) human exposure to ozone. The model accounts for time spent in different microenvironments for different age groups and incorporates long-term air quality data with high spatial resolution. The simulation results, expressed as per capita hours of exposure to ozone above various concentration thresholds, are associated with population race, ethnicity, and per capita income. The results indicate that ozone exposure differences by race and ethnicity have diminished over time. However, the study suggests that on average, low income areas may be experiencing higher ozone exposure than high income areas, suggesting that environmental health risks (e.g., respiratory diseases) may be systematically higher for low income groups in the SoCAB.