Some data and observations of primary production and hydrographic parameters have been made in the region of Ubatuba (Lat. 23º30'S Long. 45º06'W) during two seasons: summer and winter. The primary production varied from 1.01 mgC/m³ /h to 28.16 mgC/m³/h in summertime and from 0.24 mgC/m³ /h to 16.24 mgC/m³ /h in wintertime. The phytoplankton production is believed to be controlled primarily by the quantity of nutrient salts and there is a possibility that relatively nutrient-rich deeper cold waters may increase the fertility of the region.