Some novel pyridothienoxazine (5); pyridothienopyrimidines (6),(8),(9),(14); pyridothienoimidazole (16); isothiazolopyridine (17), and pyridoisothiazolopyrimidines (18– 20) were synthesized. The structural assignment of the prepared compounds were based on microanalytical and spectroscopic evidences. Some prepared compounds were tested in vitro for their antitumor and radioprotective activities. Compounds (7),(12),(17) and (19) ...