A newly developed laser scattering technique was tested for the determination of mutual solubilities in the 2-butanol + water system at moderate pressures. The liquid-liquid solubility data were measured from the region of solid-liquid equilibria to the upper critical solution temperature. Freezing points in this system were determined by a cooling curve method. A concave curvature of the liquid-liquid line was observed in the vicinity of the freezing points. The solubility data were satisfactorily correlated with Hiranuma’s modification of the Wilson equation. The newly measured data compare favorably with previous measurements.