Dinoflagellate is a main group in the marine plankton and includes both, autotrophic and heterotrophic organism. Some species are known to produce different sort of toxins which can harm also human beings. Such phycotoxins are classified according to its chemical characteristics or simptomatology into 4 groups: diarhetic shellfish poisoning (DSP), paralytic shellfish poisoning (PSP), neurotoxic shellfish poisoning (NSP) and ciguatera. DSP producing dinoflagellates are distributed into 2 genera, Prorocentrum and Dinophysis, including P. lima, D. acuminata, D. acuta, D. fortii, D. norvergica, D. mitra, D. rotundata, D. tripos, D. sacculus, D. skagii and others. Several of these species are known to occur in Brazil and DSP has been recently detected in the littoral of Santa Catarina. This paper aims to investigate the occurrence of Dinophysis at Cabeçudas beach, Itajaí, Santa Catarina. Water column samples were collected weekly from 6/01/1999 to 29/06/1999. Samples for microscopic examination were collected from the sub surface and from the water column by net tolls. Salinity, temperature, chlorophyll a and inorganic nutrients were also analyzed. Water temperature ranged from 17 to 29 oC and salinity from 25 to 36. Maximum and minimum of chl a were 3.97 and 0.83 µg.l-1, respectively. Ammonium varied from 6.85 to 12,65 µmol.l-1, while nitrate plus nitrite from 0.76 to 6.34µmol.l-1; silicate from 5.75 to 54.12 µmol.l-1 and phosphate from 0.09 to 0,82 µmol.l-1. Just 3 species of Dinophysis were observed: D. acuminata, D. rotundata e D. caudata and one Dinophysis sp. non identified. In general the abundance was low, compared to other coatings from contiguous areas, with the maximum for 80 cell.l-1 for D. caudata and D. rotundata, found in 2/02/1999 and 23/03/1991, respectively. No significant correlation among the occurrence of Dinophysis and the other variables were observed. Apart from Dinophysis, other toxic species were also observed. These results indicate that, at least during the sampled period, the abundance of DSP producers was low in the region, indicating a safe mussel extraction, considering the superior limit of 100 cell..l-1, as adopted in some countries