AbstractThe changes in total lipid content, neutral and polar lipids, total fatty acids, and free fatty acids were investigated over a 4 day period in the zygomycete,Rhizopus arrhizus Fischer. The highest concentration of lipids occurred at the 72 hr period. The degree of unsaturation in the total fatty acid fraction increased during the growth period, whereas the degree of unsaturation decreased in the free fatty acid fraction during the same time period. The ratios of neutral to polar lipids over the 4 day period were: 0.75, 0.22, 1.94 and 0.94. The major components of polar lipids were phosphatidyl ethanolamine, lecithin, lysolecithin, and fatty acids. The fatty acids in the mono‐ and diglycerides were predominately saturated (67–96%). The fatty acids in the triglycerides shifted from a predominately unaturated (69%, 24 hr) to a more saturated pattern (62%, 96 hr).