The two-dimensional distributions of the liquid phase temperatures in diesel sprays injected into high-pressure and high-temperature environments were measured using the laser-induced fluorescence technique. The liquid fuel (n-hexadecane) was doped with pyrene (C16H10). The fuel spray doped with pyrene was injected under a high-pressure of 3.1 MPa and a high-temperature of 773K. The evaporating diesel spray was excited by laser radiation at 266 nm, and the resulting fluorescence was imaged by an intensified CCD camera. The fluorescence intensity ratios of the pyrene monomer and excimer emissions have temperature dependence, and were used to determine the liquid phase temperatures in the diesel sprays. The cross-sectional distribution of the liquid phase temperature was estimated from the fluorescence images by the temperature dependence of the intensity ratio. The results demonstrate that the laser-based thermometry technique is available for planar measurements of the liquid phase temperature in evaporating diesel sprays under high-pressure and hightemperature environments.