A series of novel thiazolo derivatives 2-15 was synthesized by initial condensation of 2,6-dihydroxyisonicotinohydrazide 1 and 2-chloro-6-hydrazinylisonicotinohydrazide 11 with different organic reagents. The pharmacological screening showed that many of these obtained compounds have good anti-inflammatory, analgesic, anticonvulsant, and antiparkinsonian activities comparable to diclofenac potassium, Voltarene(®), Carbamazepine(®), and Benzotropene(®) as reference drugs. Initially the acute toxicity of the compounds was assayed via the determination of their LD₅₀. The structures of newly synthesized compounds were confirmed by IR, ¹H-NMR, ¹³C-NMR, MS spectral data and elemental analysis. The detailed synthesis, spectroscopic data, LD₅₀ and pharmacological activities of the synthesized compounds were reported.