Synthesis and antimicrobial screening with spectral analysis of some 1,3 - thiazines have been carried out in two series, first series starting material is 2- hydroxyacetophenone and we got 4-(2-hydroxy phenyl)-5-benzoyl-6-pheyl or 4-alkoxy phenyl or 4-dimethyl amino phenyl -2-imino -6-H-2,3- dihydro 1,3- thiazine(4a,4a’,4a’’,4a’’’). Second series starting material is 2-hydroxy- 5- methyl acetophenone we got 4-(2-hydroxy -5-methyl phenyl)-5-benzoyl-6- phenyl-2-imino-6 H- 2,3 dihydro-1,3-thiazine and respected derivatives as written above (4b,4b’,4b’’,4b’’’) from thiourea. All these compounds have been analyzed by melting point, IR, 1H NMR. All the synthesized compounds are tested for their antimicrobial activities.