A single ocean station was occupied for 27 hours during the Upwelling Period in Monterey Bay, California, to study light attenuation and its relation to other standard oceanographic parameters.Comparisons were made with earlier local studies.It was found that the vertical distributions of the oceanographic parameters studied are dependent on both the seasonal conditions and geographical location.The largest concentration of suspended particles was found in the upper 10-15 m of the water column where most of the light attenuation occurred.The largest attenuation gradient was found in the pycnocline.A linear relation was suggested between Uic attcr.iiGt":3r. coefficient =P n the cumulative projected cross-sectional area of the particles.Apparent relations were found between light attenuation and temperature, salinity, density, and oxygen and phosphate concentrations.