A room temperature photochemical spectrofluorimetric (RTPF) method has been developed for the assay of phenylbutazone (PB), and its major degradation products. Fluorescence spectral properties of PB, its degradation products, and their photoproducts are reported, as well as the optimal irradiation times (ranging from 4 to 45 min), which correspond to maximum fluorescence signals of photoproducts. Linear log-log calibration plots were obtained over a 50- to 1000-fold range of concentration, and limits of detection ranged between 1 ng/ml and 1.2 micrograms/ml. This has been shown to be a convenient technique, in terms of simplicity, short measurement times, sensitivity, and precision.