Tetraaza benzoxazinophenothiazine heterocyclic rings were synthesized and characterized. The key intermediate, 11-amino-6-chlorobenzo[a]-8,10-diazaphenoxazin-5-one was prepared by reaction of 4,5-diamino-6-hydroxypyimidine with 2,3-dichloro-1,4-naphthoquinone in anhydrous sodium carbonate. Whereas the parent tetraaza derivatives: 15-amino-8-bromo-6,9,12,14-tetraazabenzo[a][1,4]benzoxazino[3,2-c] phenothiazine, 9,15-diamino-6,8,12,14-tetraazabenzo[a][1,4]benzoxazino[3,2-c]pheno- thiazine and 15-amino-6,8,12,14-tetraazabenzo[a][1,4]benzoxazino[3,2-c]phenothiazine were synthesized by base catalyzed condensation reactions of 11-amino-6-chlorobenzo[a]-8,10-diazaphenoxazin-5-one with 2-amino-5-bromopyrazin-3-thiol, 4,6-diaminopyrimidine-5-thiol and 4-diaminopyrimidine-5-thiol respectively. The... compounds are intensely coloured and are readily reduced with sodium dithionite to their leuco bases which can make them applicable as vat dyes. Their wash fastness, sublimation fastness and staining undyed fabric were evaluated.