Abstract: Crassostrea oysters deployed in a long-line culture, at Guaratuba Bay, South Brazil (25° 52’ S, 48° 39’ W); were analysed in order to quantify and identify the fouling community on the shells. The effect of fouling on survival, growth, condition index and meat yield of the oysters were evaluated in a 16 week period. Moreover, a comparison was made of the growth in relation to different cleaning regime: oysters cleaned every 2, 4, 8 and after 16 weeks (control). Oysters initial and final measurements (n=480) and fouling organisms were identified and quantified at each cleaning. Survival in all treatments was similar, around 87%. A one way ANOVA was used to compare each factor (height, length, width, condition index and meat yield). After 16 weeks, the fouling had no significant effect (p > 0, 05) at none of the treatments employed. There was a tendency of growth of the oysters cleaned at every 4 weeks. The width was the factor with the higher percent of increase. Twenty five species of fouling organisms belonging to 8 taxa were identified. The most abundant organisms were: Crassostrea sp. spats (39%), followed by the barnacle Chthamalus rhizophorae (37%), the amphipod Monocorophium acherusicum (9%) and the bivalve Sphenia antillensis (8%). Polychaetes were the most abundant taxon, with 13 species. Based on this experiment, we may concluded that the fouling identified and quantified in Crassostrea sp from Guaratuba Bay, did not cause any alteration on the factors measured. Thus, the results from this work may be used by oysters producers in the studied region in order to minimize costs associated with cleaning of fouling in oysters Key words: native oyster; Crassostrea sp.; fouling community; growth; survive; Guaratuba Bay.