The key intermediate 6-Chloro/fluoro-2-aminobenzothiazole(1a,b) on treatment with hydrazine hydrate and HCl gave 6-chloro/fluoro-2-hydrazinobenzothiazole (2a,b), which on condensation with substituted aromatic aldehydes affords aryl substituted (6-chloro/ fluoro -1.3,-benzothiazole-2-yl)hydrazones(3a-j). The latter on nitrosation with sodium nitrite in acetic acid leading to ring closure and furnishes respective 8-chloro/fluoro-3-aryl- 10aH(1,2,4,5) tetrazinobenzothiazoles(4a-j). The analgesic and anti-inflammatory activity of these compounds have been carried out by Eddy’s hot plate method on Albino mice and carrageenan induced rat paw edema method. The constitutions of the products have been elucidated by IR, NMR spectral data and elemental analysis.