The objective of this study is designed to clearify the effect of marbofloxacine and ceftiofur sodium on the hepatorenal, cellular and humoral immune responses in fattening cattle calves .Twenty five baldy fattening cattle calves were divided into five equal groups (5 each).1S' group served as control, 2"4 and 3" groups were injected with therapeutic dose (Smg/kg bwt) and double therapeutic dose (10 mg/kg bwt) of marbofloxacin for three consective days respectevily, 4! and 5th groups were injected with therapeutic dose (10 mg/kg bwt ) and double therapeutic dose (20 mg/kg bwt) of Ceftiofur sodium for three consective days respectevily.At 3 day 15!, 294 and 3" week post injection ,blood samples were collected in two portions, 1st one was collected on heparinized tube for determination of total and differential leucocytic count phagocytic and killing %,2nd one was centrifuged at 3000 r.p.m.for 15 min. to separate clear serum, for determination of humoral immune response and some biochemical parameters. Both marbofloxacin and Ceftiofur sodium in both therapeutic and double therapeutic doses elucidated significant reduction of phagocytosis and bacterial killing efficiency of blood polymorphnuclear leucocytes at the 1S! and 24 week post injection. Also both drugs evoked a significant increase in total leucocytic count and neutrophil and decrease in lymphocytes at the 3" day 1St,29d and 3° week post injection Marbofloxacine in therapeutic and double therapeutic doses in fattening calves evoked a significant decline of total protein, albumin, gamma globulin, total globulin and A/G ratio, meanwhile alpha and beta globuline levels demonstrated a