The abundance, movements and behaviour of Sotalia guianensis were studied between 1999 and 2001 in the Emboraí Bay on the northeastern coast of Pará, Brazil. Dolphins are not distributed regularly around the bay and the population size is estimated to be approximately 150 individuals. Dolphins enter the bay to feed, especially at low tide. Travel, and foraging were, in that order, the behaviours most frequently observed. The potential for the conservation of the dolphins in the Emboraí Bay is good considering the absence of serious threats to the population and the fact that young and infants are regularly present, which shows that the population is reproducing.