The effects of amphotericin B (150 ㎍/㎖) and cycloheximide (10 ㎍/㎖) on the biosynthesis of phospholipid and the composition of fatty acids in chloroplasts isolated from Chlorella were analyzed. The contents of the total lipid and phospholipid (PC, PE, PI) in treatment with antibiotics were lower compared with the control. In the whole cell system, the major fatty acids utilized for biosynthesis of phospholipid were palmitic acid (31.96%) and linoleic acid (16.96%) in control while those were palmitic acid (36.15%) and linolenic acid (16.71%) in treatment with amphotericin B. And in treatment with cycloheximide, palmitic acid (31.90%) and stearic acid (15.32%) were used in phospholipid formation. The major fatty acids in chloroplasts were analyzed as to be palmitic acid and linolentic acid in control (33.75%, 18.90%) and in treatment with amphotericin B (36.75%, 9.46%). However, it was shown that the major fatty acids in chloroplasts treated with cycloheximide were palmitic acid (28.01%) and oleic acid (19.27%).