Sixteen violet-pigmented heterotrophic bacilli were isolated from Mediterranean coastal waters. Morphological and physiological studies showed that they have a number of characteristics specific to the genus Chromobacterium. However, the absence of catalase, the presence of oxidase, and, more especially, the low percentage of bases guanine and cytosine in their DNA exclude them from the genus. The specificity of some characters assigned to Chromobacterium can thus be discussed. Several features allow us to consider such bacteria as being related to the genus Alteromonas; their consistency within the 16 strains investigated leads us to consider them as a single species, for which the specific name Alteromonas luteo-violaceus (sp. nov.) is proposed.