A two-year systematic survey was conducted in a rocky exposed shore located at Porto das Baleias (São Vicente, Capelas) in the north coast of São Miguel Island and supposedly representative of the Azorean rocky shores. Zonation of the littoral molluscs (Gastropoda, Bivalvia and Polyplacophora) was established for the most abundant species and possible molluscs/algae biological associations were studied. Seventy-one taxa (56 Gastropoda, 13 Bivalvia and 2 Polyplacophora) were found in the 1996 and 1997 fieldwork, with a total of 35,960 specimens recorded. Bittium sp., an Azorean endemism, was the commonest taxon, with 11,936 and 12,374 individuals (61.1% and 75.4%, respectively in 1996 and 1997). Thirteen taxa accounted for about 96% of the total of specimens collected in both years. Some differences in the relative abundance of the commonest taxa were found between the two years. Besides Bittium sp., the next most abundant taxa in 1996 were Tricolia pullus azorica (14,0%), Jujubinus pseudogravinae and Manzonia unifasciata, both with 4%, and Parvicardium vroomi, Alvania sleursi and Crassadoma pusio, all between 2-3%. In 1997, P. vroomi and T. pullus azorica (6,4% and 6,1%) were the most abundant species after Bittium sp., followed by Alvania sleursi and Jujubinus pseudogravinae with a little more than 1% of the total number of molluscs collected in that year. The endemic rissoids Alvania angioyi, Manzonia unifasciata and Rissoa guernei, the also endemic trochid Gibbula delgadensis, the Macaronesian Anachis avaroides and the small bivalve Parvicardium vroomi were only abundant in shallow levels (down to 5-6m), whereas the endemic rissoid Alvania sleursi is especially abundant below 20m depth. Bittium sp., Tricolia pullus azorica and Jujubinus pseudogravinae were found along all transect. No specific molluscs/algae associations were found.