Abstract: An experiment was conducted to detect the relationship between some serum enzyme activities, i.e. lactate dehydrogenase (LDH) and creatine phosphokinase (CPK) enzymes and liver functions, as well as evaluating the difference in some physiological parameters in relation to body weight in six body weight lines of Golden Montazah (GM) chickens. A total of 288 GM chickens 4-wk old were selected from 500 unsexed GM chickens and divided into six lines (three lines within each sex) heavy (HL), light (LL) and control (CL) according to their body weights. Each line was represented by 3 replicates (16 chicks each) over two generations (G0 and G1). Live body weight (LBW), body weight gain (BWG), mortality rates and the levels of some serum parameters, i.e. total protein (TP), triiodothyronine (T3), LDH, CPK, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were determined at 4 WOA in G0 and at 12 WOA in G0 and G1. The results showed that the average LBW and BWG for heavy lines and males were significantly (p<0.01) higher than that of light lines and females, respectively. The heavy line chicks recorded the lowest mortality rate compared to the light ones during the period from 4-12 WOA over the two generations. The HL body weight was associated generally with an increase in the serum TP, T3 level and LDH activity and a decrease in AST, ALT and CPK activities as compared with the LL body weight. Converse trend was observed for these traits with the LL chicks. These results concluded that, it is possible to use these parameters as physiological indices to attain the goal of improving meat production and to produce a safety and healthy poultry production.