A new gradient reverse phase high performance liquid chromatography method has been developed for quantitative determination of related substances of Diacerein (DA) and Meloxicam (MC) in pharmaceutical dosage forms. Chromatographic separation achieved on a column L1, C18 250 mm x 4.6 mm; 5 μm with 0.02M sodium acetate pH 4.5 buffer as mobile phase-A and Acetonitrile and water (9:1) as mobile phase–B at a flow rate of 1.0 mL min-1. Diluent as mobile phase A and tetrahydro furan of ratio 50:50 v/v with detection at 254 nm and 310 nm. The injection volume was 20 μL and a gradient program with run time of 90 minutes. The developed method validated according to ICH guideline with the parameters specificity, forced degradation (with stress conditions of acid, base, oxidative hydrolysis, thermal and photolytic degradation), limit of detection and limit of quantification, linearity, precision, intermediate precision, accuracy, robustness and ruggedness. From all validation parameters results the method proved as spec ific, stability indicating, precise, accurate, robust and rugged metho