Rod outer segments purified from bovine retinal homogenates were incubated with radiolabelled fatty acids (palmitic, docosahexaenoic) and palmitoyl Coenzyme A, and were found to contain enzyme activities that catalyze addition of these compounds to the major phospholipids of rod outer segment membranes. It is suggested that these phospholipid retailoring enzymes function to establish the unique fatty acid distribution and composition of the phospholipids of vertebrate rod outer segment membranes.