Simple, rapid and economic Spectrophotometric method was developped for the assay of certain proton pump inhibitors (PPIs) belonging to benzimidazole derivatives namely; omeprazole, rabeprazole, pantoprazole and lansoprazole. The method depends on the reaction of the cited proton pump inhibitors with diazotized p-nitroaniline in alkaline medium using 1.5 N NaOH and dimethylformamide. The produced green color was measured at 590 nm for omeprazole, rabeprazole and 610 nm (for, pantoprazole and lansoprazole). The recorded absorbances obey Beer's law for 5-30, 10-35, 5-40 and 5-40 μg ml-1 omeprazole, rabeprazole, pantoprazole and lansoprazole, respectively with good correlation coefficients (0.9996-0.9999). The limits of detection and quantification are also reported for the studied method. Intra-day and inter-day precision as well as accuracy and robustness of the method have been evaluated. The proposed method was successfully applied to the assay of the studied proton pump inhibitors in pharmaceutical dosage forms and the results were statistically compared with those of reported method by applying Student’s t-test and F-test where no significance differences were observed.