Readily extractable lipids of Pseudomonas diminuta constituted about 14% of the cell dry weight. The total lipids were separated into two fractions, soluble and insoluble in ethereal chloroform. The insoluble fraction consisted mainly of polyβ-hydroxybutyrate. The soluble fraction (about 75% of the total lipids) consisted mainly of a mixture of three glycolipids and two phospholipids. The glycolipids belonged to the class of 1-O-glycosyl diglycerides, and were identified as 1-O-α-d-glucopyranosyl-d-2,3-diglyceride, 1-O-α-d-glucopyranuronosyl-d-2,3-diglyceride and 1-[O-β-d-glucopyranosyl-(1→ 4)-O-α-d-glucopyranuronosyl]-d-2,3-diglyceride. One of the phospholipids was phosphatidylglycerol, the other appeared to be a new phosphoglucolipid. Analytical and chromatographic data for the latter compound indicated that it was a phosphatidyl derivative of a glucosyl diglyceride. Palmitic acid and an octadecenoic acid accounted for about 95% of the fatty acid content of the phospholipids and the monoglycosyl diglycerides, but the diglycosyl diglyceride had an enhanced content (about 11%) of a nonadecenoic acid. © 1969.