This work involves synthesis of different five, six and seven membered heterocyclic rings starting from 2-hydrazino benzothiazole which was synthesized from the corresponding 2-mercapto benzothiazole on its reaction with hydrazine hydrate. This is work is divided into four different parts: First part: This part involved the synthesis of oxadiazole, oxazoline, triazole, thiadiazole and diazole from compounds [a], [1] and [19] with different organic materials as shown in Schemes (1) and (2). Second part: This part involved the synthesis of phthalazin and pyridazin-3,6-dione derivatives from the reaction of compound [1] with succinic, maleic and phthalic anhydrides as shown in Scheme (1). Third part: This part involved the synthesis of two new Schiff bases derived from the reaction of compound [1] with two aromatic aldehydes and cyclization by the treatment with mercapto acetic acid and maleic anhydride resulted oxazepines [9, 12] and thiazolidins [10, 13] respectively as shown in Scheme (1). Fourth part: This part deals with the study of antibacterial activities of some of the synthesized compounds and comparing these activities with that of the starting materials. These activities were determined in vitro using well diffusion method against two types pathogenic strains of bacteria Staphylococcus Aureus (G+) and Proteus Vulgaris (G-). The results revealed that some of these compounds showed measurable activity as shown in Table (3-2).