High dynamic range mass spectrometry measurements of 135Cs (T(subscript 1/2)~2.3) Myr) in 1956, 1963, and 1965 rain samples from southern California gave an initial 137Cs/135Cs ratio of ~0.83, which is more consistent with the production ratios of 239Pu (0.87) than those from 235U. Cesium isotope profiles were also determined for the top of a sediment core from the Santa Monica Basin off the coast of Southern California. The sedimentary 137Cs/135Cs are generally consistent with these findings, but in detail do indicate some disturbances between the fallout Cs from different years.