Lead chalcogenide diode lasers are useful for spectroscopic and fiber optics applications in the mid-infrared (2.5-30 μm) wavelength range. These devices have previously required cryogenic cooling (<100 K) for CW operation. This limitation has been overcome through the use of a new, lattice-matched alloy system, Pb1-xEuxSeyTe1-y as well as the introduction of advanced, quantum well active region device structures grown by molecular beam epitaxy (MBE). Operating temperatures have been increased to 175 K CW (at 4.4 μm) and to 270 K pulsed (at 3.9 μm). Thermal leakage currents out of the device active region appear to be limiting device performance. This has led to the study of band offsets in PbEuSeTe/PbTe heterojunctions as well as to exploration of alternative high energy band gap alloys of PbTe with Ge, Yb, Ca, Sr, and Ba. The status of this work and examples of ultrahigh resolution studies done with these tunable laser sources will be included.