Raman spectroscopic, X-ray diffraction and EXAFS measurements have been carried out on (As 2S 3) 1− x (GeI 4) x glasses, with 0.0⩽ x⩽0.4. The I atoms incorporated into the As 2S 3 glass are preferentially bonded to As atoms and form AsI 3 molecular units. Three structural units, AsS 3/2, AsI 3 and partially I-substituted GeS 4/2 units, are present in the system. The As–S and Ge–S bond distances are almost identical to their covalent distances, while the As–I distance is nearer to the ionic distance. The detection of Ge–I bonds from extended X-ray absorption fine structure (EXAFS) measurements infers the existence of mixed-anion type units, such as Ge(S 3/2I) tetrahedra. The coordination numbers of the constituent atoms in the system, obtained by least squares analysis, are approximately 4 for Ge, 3 for As, 2 for S and 1 for I.