The lipid compositions of infected (Glomus mosseae) and noninfected fibrous roots of sweet orange, sour orange, rough lemon, Carrizo citrange, Cleopatra mandarin and Rangpur lime were studied. Infected roots of all cultivars contained significantly more phospholipids and triglycerides than did their noninfected controls. Campesterol was found at significantly higher percentages of free sterols, whereas cholesterol and β-sitosterol were detected at lower percentages in infected roots when contrasted to their respective controls. Three unknown fatty acids (A, B, and C) were detected in infected roots but not in noninfected roots. Unknowns A, B and C made up 46 to 52 % of the fatty acids in the triglycerides, 31 to 41 % in the total lipids and 7 to 20 % in the phospholipids.