Chalcohalide glasses are mixtures of chalcogenides and halides. This paper reviews the properties and structure of various glass-forming chalcohalide systems. These materials possess high transmittance in the infrared, which make them candidates for various applications in the area of infrared fiber optics. In general, the packing density, glass transition temperature (Tg), and refractive indices decrease with the addition of a halogen component into binary chalcogenide glasses. It also seems to be theoretically possible that the attenuation loss of the glasses and fibers, especially at 10.6 μm, decreases at the same time. The observed changes in the properties of glasses are in good agreement with the proposed structural model, suggesting degradation of the network connectivity by the addition of network-terminating halogen atoms.