We report on the first demonstration, to the best of our knowledge, of continuous-wave (cw) mid-infrared generation from laser difference-frequency mixing in a LiInSe2 crystal (lithium indium selenide, or LISe) in the X-Y plane. Two Ar+ laser-pumped Ti:Sapphire lasers were employed as widely tunable pump sources. A LiInSe2 crystal (7 mm × 6 mm × 9 mm) cut at φ = 54.75° and θ = 90° was used as frequency down-converter. The infrared spectral region of 6.2-7.5 Um has been covered with angle and wavelengths tuning by type II (eoe) critically phase-matched parametric interaction (Figure 1). The phase-matching (PM) conditions in the cw difference-frequency generation (DFG) process have been investigated. Based on the measurements of relative values of the power conversion efficiencies for LISe-and AgGaS2-based DFG, the effective nonlinear coefficient deffof 12.1 pm/V for LiInSe2 at ∼ 7 μm has been determined relative to the well known nonlinearity coefficient d36 of AgGaS2 , which yields a power conversion efficiency of about 29.8 μW/(W2.cm). The accessible infrared wavelength range is important for molecular spectroscopic studies and we will discuss the performance of this new laser source for trace gas sensing applications.