The first room-temperature operation of an interband III-V laser diode emitting at a wavelength beyond three microns was demonstrated recently at the Naval Research Laboratory in Washington, D.C. This achievement brings the gallium-antimony(GaSb)-based technology closer to achieving truly practical and portable mid-infrared systems that are needed for many military and commercial applications. A truly practical mid-infrared laser will need to operate continuously at room temperature to find widespread commercial acceptance. The opto-electronics community has worked toward this goal for more than a decade. Inexpensive room-temperature laser diodes ultimately will find widespread use in such applications as pollution monitoring, leak detection, medical diagnostics, factory process control, base-cleanup, and the detection of chemical weapons sites.