Two stability indicating methods have been developed for determining rofecoxib in the presence of its degradation product. The first suggested method is high performance liquid chromatography (HPLC), in which analysis is carried out using hypersil BDS C18 column (250 × 4.6 mm I.D.) with mobile Phase consisting of 0.05 M phosphate buffer (pH 3.5) and acetonitrile (70:30 v/v). A linear relationship was obtained between the detector response at 225 nm and the corresponding concentration of the studied rofecoxib in the concentration range (1–6 μg / 10 μl) with mean % recovery of 99.80 ± 0.405. The second method depends on the quantitative densitometric evaluation of thin layer chromatograms (HPTLC) with mobil phase consisting of toluene: chloroform: methanol (60: 35: 5 v/v/v) by using fluorescent high performance silica gel 60 plate. A linear relationship was obtained between peak area and the concentration of the cited drug in the range 1–6 μg/spot with a mean % recovery of 99.79 ± 0.185. The suggested methods are precise, accurate, rapid and prove their specificity in the presence of its degradation products. Both procedures are successfully applied to determine the drug in the presence of its degradation product and also in their pharmaceutical formulations.