Gas chromatographic and mass spectrometric analyses were made of the aliphatic hydrocarbons and fatty acids of Vibrio marinus, MB-22 (a marine vibrio) and a blue-green alga Anacystis nidulans. The Vibrio marinus, an obligate psychrophile was grown at four different culturing conditions: (1) 5°C/ anaerobic, (2) 5°C, aerobic, (3) 15°C, anaerobic, and (4) 15°C, aerobic. The marine vibrio, MB-22, a mesophile, was also analyzed for its hydrocarbon and fatty acid content at 30°C. The Anacystis nidulans, a moderate thermophile, was analyzed at 23°C and 39°C. It was demonstrated that there were significant changes in both the total content and the relative percent of the individual aliphatic hydrocarbon components of the cells analyzed. Such changes were attributed to the variations in the culturing conditions. Only moderate differences were observed for the fatty acid content of the same cells. However, the cells grown under anaerobic conditions showed considerably higher total lipid content than those grown aerobically.