The characteristics of tunable Pb1−xSnxTe(0.08⪝×⩽∼0.20)junction lasers are described. The lasers operate cw at liquid‐helium temperatures and for the above alloy compositions, the wavelength is in the 8–12‐&mgr;m region of the infrared. The devices are prepared by antimony diffusion into largep‐type vapor‐grown single crystals. Active region width, gain, and loss parameters are derived from measurements of the current density at the lasing threshold, efficiency, and cavity length dependence of the threshold current. Impurity diffused lasers favor oscillation in high‐order TE modes and some evidence of filamentary lasing was obtained from the device parameters together with a study of far‐field patterns. Results are presented which confirm the model of current tunability of these devices and provide data on refractive index and temperature dependence of the forbidden energy gap in these alloys. Finally, spectroscopic data are presented to show the present limitations and potential of the diode laser for rapid(≪50 &mgr;sec)high‐resolution gas spectroscopy.