The organic sulfur content of suspended and sinking particulate matter was examined in the upper 1000 m of the water column in the Southern California Bight. Depth distributions of suspended particulate organic sulfur (POS) showed a subsurface maximum in most stations that deepened offshore. POS concentrations in suspended matter averaged 1.26 ± 0.50 μg S L−1within the euphotic zone during the two cruises analyzed (August and October, 1987). The downward fluxes of mass, carbon, nitrogen and sulfur of sinking particulate matter increased with increasing sample depth to 350 m in the water column. Fluxes were similar during the three deployments. POS was correlated with and directly proportional to POC, PON, and chlorophyllain the suspended material. Similar correlations were obtained in the trap material although a positive POC intercept value suggested the presence of more refractory material, with sulfur being selectively removed relative to carbon. The average molar ratios were C : N : S = 224 : 27: 1 in suspended and 119 : 17 : 1 in sinking particulate organic matter. Particulate organic sulfur appeared to have a biological origin, most likely plankto