Recent measurements in the Central Transverse Ranges of southern California suggest possible correlations of changes in groundwater radon content with occurences of nearby earthquakes. Since measurements began in 1974, three radon anomalies have been accompanied by subsequent nearby seismic events. Two of these anomalies were associated with moderate-sized earthquakes and one with a swarm. Within a 60-day window prior to the seismicity, groundwater radon increased in each case at sites close to the earthquake epicenters. Before the Big Bear earthquake of June 30, 1979 (M = 4.8), radon anomalies were found at three nearby monitoring sites. Groundwater radon content at one site near the January 1, 1979 Malibu earthquake (M = 5.0) showed negative as well as positive anomalies both prior to and following the earthquake. A radon anomaly occurred at a nearby spring prior to the fall 1976 Palmdale swarm. The observed pattern is similar to pre-earthquake anomalies reported from Russia, China, and Japan.