Pyridazine and pyrazole ring systems are known to possess potent biological and pharmacological properties. On the other hand some pyridazines derivatives are used as key starting material for the synthesis of commercial dyes. Acetylacetone, ethyl acetoacetate and malononitrile were coupled with diazotized arylamines to give arylazoacetylacetones, ethyl arylazoacetoacetates and arylazomalononitriles; these when refluxed with 5,6-diphenyl-2,3-dihydro-3-oxopyridazine-4-carbohydrazide, 3-amino-4,5-diphenyl-1H-pyrazolo[3,4-c]pyridazine and 3-hydrazino-4,5-diphenyl-1H-pyrazolo[3,4-c]pyridazine yielded the corresponding 4-[(3-arylazo-3,5-dimethylpyrazol-1-yl)carbonyl]-5,6-diphenylpyridazin-3(2H)-one, 7-arylazo-6-methyl-3,4-diphenylpyrimido[1`,2`:1,5]pyrazole[3,4-c]pyridazin-8(5H)-one and 2-(4,5-diphenyl-1H-pyrazolo[3,4-c]pyridazin-3-yl)-4-arylazo-1,2-dihydro-5-methyl-3H-pyrazol-3-one dyes respectively. The dyes were applied to polyester and polyamide fabrics, and their spectral and fastness properties measured.