The aim of the present work is the synthesis of new derivatives of N-substituted 10H phenothiazine. To obtain these derivatives, the diphenylamine was chosen as the starting material which was heated for 5hrs. with sulfur in presences of iodine, it gave the phenothiazine (1). 1- Reaction of phenothiazine with chloro acetyl chloride gave N10- (chloro acetyl) phenothiazine (2), which was treated with hydrazine hydrate to give N10- (acetyl phenothiazine) hydrazine (3) which is the desired product. The hydrazine derivative (3) was reacted with carbon disulfide in presence of KOH to give potassium N10-(acetyl phenothiazine) dithiocarbazate (4) which was refluxed with hydrazine hydrate to give N10-(4-amino-3-mercapto-[1H]-1,2,4- triazin-5-yl)] phenothiazine (5). 2- N10-(3-mercapto-[1H,6H]-1, 2, 4-triazin-5-yl) phenothiazine (7) was obtained from the reaction of phenothiazine (1) with thiosemicarbazide to give N10-(acetyl phenothiazine) thiosemicarbazide (6) which suffered intramolecular cyclization when refluxed with basic media ( 2N NaOH) for 3hrs. to give triazine derivative (7). 3- Treatment of phenothiazine (1) with thiourea gave N10-(acetyl phenothiazine) thiourea (8), which was used for the preparation of two types of heterocyclic derivatives: A- The compound N10-(2-amino-[5H]-1, 3-thiazol-5-yl) phenothiazine (9) was synthesized by the intramolecular cyclization of thiourea derivative (8) which was refluxed with conc. H2SO4 for overnight. B- N10-(2-mercapto-[5H]-1,3-imidazol-4-yl) phenothiazine (10) was synthesized by the intramolecular cyclization of thiourea derivative (8) through its reflux with (2N NaOH) for 3hrs. 4- Synthesis of N10-[2-([5H]-1, 3-imidazol-4-yl) hydrazine] phenothiazine (11) was obtained from the reaction of compound (10) with hydrazine hydrate. 5- Schiff's bases: compounds {N10-[(2-[5H]-1, 3-imidazol-4-yl) hydrazone] phenothiazine [12-14]} have been synthesized from the reaction of compound (11), with different aromatic aldehydes. 6- N-[N10-(acetyl phenothiazine)]-4-nitrophenyl hydrazine (15) was synthesized by the reaction of N10-(chloro acetyl) phenothiazine (2) with 4-nitrophenyl hydrazine, which then was treated with phenylisocyanate to give 4N [N10-(acetyl phenothiazine)]-1-phenyl-3-p-nitrophenyl semicarbazide (16). 7-N10- (3- N- phenyl-4- p- bromophenyl-2- hydroxy-4- oxazolin-2- yl) acetyl -2N-nitrophenyl hydrazine (17) was synthesized by the intermolecular cyclization of compound (16) with 4-bromophenancyl bromide. 8- Aryl amino acetyl N10-phenothiazine (18-23) were obtained from the reaction N10-(chloro acetyl) phenothiazine (2) with different aromatic amines under refluxing condition.