Planar laser-induced fluoresence is used to study the mixing of a heated inlet water stream injected into a tank of water that is initially at a uniform temperature. The water contains a mixture of two dyes, temperature-sensitive rhodamine 560 and temperature-insensitive sulforhodamine 640. A planar sheet of frequency-doubled 532-nm laser radiation from a Q-switched Nd:YAG laser is used to excite the fluorescence emission. Temperature is determined from the ratio of fluorescence emission from these two dyes. The processed images shown here allow us to study in detail the mixing of the heated inlet stream in the water tank. For details, see the paper by Robinson et al., pp. 2852-2858.