Room temperature electroreflectance measurements in the region of the lowest direct exciton were performed on the system GaSe1-xTex in the full composition range. A discontinuous jump in the dependence of exciton energy and broadening parameter occurs in the molar fraction range 0.26 ≤ x ≤ 0.60. This supports previous Raman measurements on these solid solutions which suggested the existence of two distinct phases: an hexagonal phase for x ≤ 0.26 and a monoclinic phase for x ≤ 0.60. Detailed study of broadening parameter as a function of molar fraction in the hexagonal phase suggests that the alloys have an indirect edge for low tellurium concentration but become direct as the latter increases. Line width considerations locates the crossing point between direct and indirect gaps at x {reversed tilde equals} 0.11, in good agreement with predictions made on volume change using the behaviour of direct and indirect edges in the alloy system GaSe1-xSx. © 1976.201111011105Kuhn, Chevy, Chevalier, (1975) Phys. Status Solidi (a), 31, p. 469. , and references thereinSemiletov, Vlasov, (1964) Sov. Phys. Cryst., 8, p. 704Kristallografiya (1963) Kristallografiya, 8, p. 877CERDEIRA F., MENESES E.A. & GOUSKOV A. (to be published)Aulich, Brebner, Mooser, Indirect Energy Gap in GaSe and GaS (1969) physica status solidi (b), 31, p. 129Suzuki, Hamakawa, Kimura, Komiya, Ibuki, (1970) J. Phys. Chem. Solids, 31, p. 2217Grandolfo, Gratton, Anfosso Somma, Vecchia, Exciton binding energies of layer-type semiconductors GaSe and GaTe (1971) Physica Status Solidi (b), 48, p. 729Grasso, Mondio, Pirrone, Saita, (1975) J. Phys., 8 C, p. 80Mercier, Mooser, Voitchovsky, (1973) J. Luminesc., 7, p. 241Gaveleshko, Kurik, Savtchuk, Delevskh, Exciton Absorption in GaSxSe1−x Solid Solutions (1974) physica status solidi (b), 65, p. K19Schluter, Camassel, Kohn, Voitchovsky, Shen, Cohen, Optical properties of GaSe and GaS_{x}Se_{1-x} mixed crystals (1976) Physical Review B, 13 B, p. 3534Shaklee, Pollack, Cardona, (1965) Phys. Rev., 15, p. 883Aspnes, Rowe, (1971) Phys. Rev. Lett., 27, p. 188Alibert, (1973) Ph.D. Thesis, , Université des Sciences et Techniques du Languedoc, Montpellier, France, (unpublished)MENESES E.A., JANNUZZI N., FREITAS J.R. & GOUSKOV A. (to be published)Cardona, (1963) Phys. Rev., 129, p. 69Thompson, Cardona, Shaklee, (1966) Phys. Rev., 146, p. 601Paramenter, Energy Levels of a Disordered Alloy (1955) Physical Review, 97, p. 587Van Vechten, Bergstresser, (1970) Phys. Rev., 1 B, p. 3351Woolley, Warner, OPTICAL ENERGY-GAP VARIATION IN InAs–InSb ALLOYS (1964) Canadian Journal of Physics, 42, p. 1879Besson, Jain, (1974) Proc. 12th Int. Conf. Phys. Semicond., p. 987. , M.H. Pilkuhn, Teubner, StuttgartMercier, Mooser, Voitchowsky, (1975) Phys. Rev., 12 B, p. 4307Fano, (1961) Phys. Rev., 124, p. 1866