Granulomatous inflammation was induced in rats by subcutaneous implantation of formalin-soaked filter paper and lipid classes in inflammatory tissue were investigated. An increase in triglyceride content was observed in parallel with the formation of adipose tissue in the early stage of inflammation. In the stage of growth of granulomatous tissue, phospholipids increased with the gradual decrease in triglyceride content. In the early stage of granulomatous tissue formation, triglycerides contained mainly saturated fatty acid (16:0) and unsaturated fatty acids (18:1 (ω-9), 18:2 (ω-6) and 18:3 (ω-3)). Phospholipids in the growing stage of granulomas contained mainly polyunsaturated fatty acids (20:4 (ω-6) and 22:4 (ω-6)). Rapid and selective in vitro and in vivo incorporation of radio-labelled unsaturated fatty acids (20:3 (ω-6), 20:4 (ω-6), 20:5 (ω-3)) into phospholipids was observed in granulomatous tissue. These results suggested that fatty acids released by lipolytic degradation of triglycerides in adipose tissue in the early stage of granulomatous inflammation are converted into phospholipids in cells accumulating in maturing granulation tissues, and also that these dynamic changes in lipid metabolism play important roles in the progress of inflammatory processes.