A rapid and efficient method for the preparation of some new pyrimidine, pyrazoline and isoxazoline derivatives by the reaction of chalcones with hydroxylamine, urea and hydrazine hydrate under microwave exposure has been reported. The products have been isolated, purified and characterized by spectral methods like IR, NMR and mass spectrometry. The antibacterial and antifungal activities of the final products against various bacteria and fungi have also been reported