This paper deals with the sudden inhibition of the colonization of oysters and barnacles in the Jacuruna River estuary (Station I) and the Itaparica Channel (Station II) - Bahia, which occurred in October, 1977 to January, 1978. Experimental panels cementamianthus were installed in October, 1976 and were followed through 19 months in the two statios. The organisms fixed on those panels were counted, and their inhibition rate was calculated form the settling density (Bourget & Lacroix, 1972). The cirripeds Balanus amphitrite amphitrite, Chthmalus sp. and Euraphia rhizophorae cohabited with the oister Crassostrea rhizophorae in both stations. The influence of biotic and abiotic factors was discussed. The authors admitted that some environmental alteration, probably of chemical origin, has affected the settling density on the experimental panels.