Hyperlipidemia is one of the most important factors leading to atherosclerosis and heart disease, therefore, this study conducted to examine the effect of two newly synthesized compounds[3-(5(ethylthio)-1,3,4-thiadiazol-2-yl)-2,3-dihydro-2-(3-nitrophenyl)benzo[1-3-e] thiazin-4-one (I) and 5(4dimethyl amino) benzylidene amino)-1,3,4-thiadiazole-2-thiol(II)] on the activities of creatine kinase(CK) and 3-hydroxy-3-methylglutaryl- CoA reductase (HMGR) in male Wister mice . Also to determine the type of inhibition of these compounds on the above enzymes .The study was carried out on sixty male Wister mice aged seven to eight weeks their weight ranged(180-200 g) . The mice were grouped as: group(1): control group (12 mice).Group(2):consisted of 48 mice in which the mice were daily administered cholesterol (25mg/kg/day) in coconut oil 6% and creamy cheese for 28 days. Lipid profile was measured for 12 of mice chosen randomely from G2 to assure hyperlipidemia. Then group2 is subdivided into three groups as:group (2.A): (12 mice) positive control group in which the mice were daily administered simvastatin (40mg /day) as standard drug for hyperlipidemia for 20 days.Group(2.B):(12 mice) in which the mice were daily treated with (10-4)M of compound (I)via drinking water for 20 days. Group(2.C):(12 mice) in which the mice were daily treated with (10-5)M of compound II via drinking water for 20 days.Lipid profile(Tch, TG, HDL-c, LDL-c and VLDL-c) were determined in all groups.The activities of CK and HMGR were determined in all groups. Lineweaver-Burk plot was used for determination of Vmax, Km and type of inhibition for treated and untreated groups with compounds I and II. The results showed significant elevation in levels of Tch, TG, LDL and VLDL, while there are significant reduction in HDL-c levels in G2 comparing to control group(G1), after administration of fat rich diet. Simvastatin, compound I with concentration (10-4M) and compound I The results revealed that the levels of Tch, TG, LDL and VLDL were reduced while the levels of HDL-c was elevated after administration of simvastatin, compound I and II in G2A, G2B and G2C respectively. The results showed that the activities of CK reduced for group G2B and G2C while it is increased for G2A . The results also showed that the activities of HMGR were reduced in the three groups. The effect of compound I on CK activity was found to be noncompetitive inhibitor with Vmax values values(1000and 166.6) U/L respectively for the uninhibited and inhibited reactions and Km value (0.6)mmol/L for compound I and with Vmax values (1000 and 250)U/L and Km value(0.84)mmol/L respectively for the uninhibited and inhibited reactions for compound II. Compounds I and II were found to be noncompetitive inhibitors on HMGR with Vmax values (0.83 and 0.16)U and Km value (0.34)mmol/L respectively for the uninhibited and inhibited reactions for compound I and Vmax values (0.83 and 0.35) U and Km value(0.28)mmol/L respectively for the uninhibited and inhibited reactions for compound II. In conclusion the new compounds(I and II) showed different inhibitory effect on CK and HMGR activities that could be used in treatment of hyperlipidemia and related disease in future.