The cellular phospholipids (PLs) and fatty acids (FAs) were investigated in type and environmental strains of Pseudoalteromonas, Alteromonas macleodii, A. infernus, and in three type strains of Marinomonas, M. communis, M. vaga, M. mediterranea. A total of 40 strains (19 strains in this study and 21 reported in previous papers), including Idiomarina abyssalis, I. zobellii, and Glaciecola punicea, G. pallidula, aerobic Alterornonas-like proteobacteria showed genus-characteristic patterns of phospholipids and fatty acids useful for genera discrimination. The PL patterns of surface cultures of alteromonads, pseudoalteromonads, and marinomonads consisted almost entirely of phosphatidyl ethanolamine and phosphatidyl glycerol presented in different proportions. Neither diphosphatidyl glycerol nor glycophospholipids were found in bacteria studied. In addition, the minor amount of a glycolipid was found in all strains studied. Bacteria of the genera Marinomonas, Idiomarina, and Glaciecola were clearly distinguished by presence of one of the major FAs: 18:1 (n-7), i15:0, and 16:1 (n-7), respectively. The amounts of these FAs reached up to 40-60% of total FAs. Members of Alteromonas and Pseudoalteromonas were characterized by different ratio of the following major FAs:16:1(n-7), 16:0, 17:1(n-8), and 18:1(n-7).