Two rapid assay procedures based oil visible spectrophotometry and high performance liquid chromatography (HPLC) have been developed for lansoprazole in bulk drug and in capsules. Spectrophotometric method is based oil the formation of a charge-transfer (CT) complex between chloranilic acid (CAA) as a pi-acceptor and lansoprazole (LPZ) as ail n-donor in acetonitrile solvent, the absorbance of the complex being measured at 520 nm. Beer's law is obeyed for 5-80 mu g mL(-1) with an apparent molar absorptivity of 3.45x 10(3) L mol(-1) cm(-1) and a Sandell sensitivity of,0.0011 mu g cm(2).. The HPLC determination was performed oil a reversed phase column (Hypersil C-18 5 mu m; 250X4.6 mm. i.d) using a mobile phase (1 mL min(-1)) consisting of acetonitrile-0.1% phosphoric acid (pH 3)-70:30(v/v) with UV-detection at 284 nm. A reactilinear relationship between mean peak area and concentration of LPZ was observed in the range 6-248 mu g mL(-1) with a detection limit of' 0.62 mu g mL(-1) and a quantitation limit of 1.86 mu g mL(-1). Intra-day and inter-day precision, and accuracy of the methods have been established according to the Current ICH guidelines. The methods have been successfully applied to the assay of LPZ in tablet preparations with recoveries varying from 97.14 to 102.3% with standard deviation in the range of o.57-1.65%, The results were statistically compared with those of the reference method by applying Student's t-test and F-test. Accuracy, evaluated by means of the spike recovery method was in the range 97.66-106.6%, with precision (RSD) better than 3%.