A preliminary characterization of macrozoobenthic assemblages on the continental shelf off southwestern Santa Marta, Colombian Caribbean, is made on the basis of bottom samples taken at 17 stations, in depths between 15 and 100 m. Only families of the most abundant groups, Mollusca and Polychaeta, were taken into account for the analysis. Cluster analysis of similarity between stations and between families revealed the ocurrence of three assemblages, whose spatial distribution is related with sediment type, depth, and some biological features: one assemblage is found on bottoms with fine to very fine sand and muds at dephts between 15 and 60 m, showing the greater abundances and families diversity; the second assemblage is found at about 60 m depth in muddy bottom; a last assemblage inhabits also muddy bottom below 100 m depth and exhibits the lowest numbers of abundance and diversity.