Phyllophaga ravida Blanchard and Phyllophaga opaca Moser (Coleoptera: Scarabaeoidea: Melolonthidae) are economically important in Mexico. An option for management of the insect pests is use of sex pheromones. To obtain the chemical profile of sex pheromones of both species the posterior section of the genital chamber of females was excised and macerated to release the contents. Eight compounds from P. ravida were identified by retention index and mass spectra: cyclohexane, 1,1′-(2-tridecyl-1,3-propanediyl) bis-; 10-methyl-eicosane; 5-butyl-hexadecane; 3-hexen-2-one; 3,3-diethyl-azetidine-2,4-dione; tetramethyl-oxirane; 3-methyl-2-pentanone; and 2-methoxy-2-methyl-butane. Seven compounds were identified for P. opaca: cholesta-4, 6-dien-3-ol; cholesterol; cholesta-3,5-dien; 2-methyl heptadecane; α-tocopherol succinate; 9,19-cyclolanost-24-en-3-ol, acetate; and lup-20 (29)-en-3-ol, acetate. Some identified chemicals, mainly 3,3-diethyl-azetidine-2,4-dione and 2-methyl heptadecane might be involved in sexual attraction of P. ravida and P. opaca, respectively. Several compounds probably are incorporated from plants into insects during feeding, and further transformed by metabolism.