Grey Mullet Mugil cephalus L, fingerlings were chronically exposed to sub lethal concentrations of lead (Pb) (0.1 and 0.4 mg/L for twenty-eight. The changes in the leucocytes and serum glucose, protein, and total cholesterol of the fish were determined every seven days in a renewable static bioassay system. At the end of the study, these parameters were significantly (p<0.05) elevated in the Pb - exposed groups when compared with the control group. Showing a pronounced leuocytosis in the Pb-exposed fish. The magnitude of increase was influenced by increasing of exposure period and Pb concentration. The Pb exposed fish were significantly (p<0.05) hyperglycemic and hyperbcholesteremic. The serum glucose levels on the 7th day were 26.50 ± 2.12 g/dL and 30.50 ± 0.70 g/dL in the fish exposed to 0.1 and 0.4 mg Pb/L respectively. On the 28th day, the serum glucose concentrations were 52.50 ± 2.12 and 70.00 ± 2.83 g Pb/dL in the groups exposed to 0.1 and 0.4 mg Pb/L, respectively. The cholesterol concentration increased from 113.5 ± 3.53 mg Pb/dL on day 7 to 208.0 ± 1.80 mg/dL on day 28 in the group exposed to 0.1 mg Pb/L. When the fish was exposed to 0.4 mg Pb/L lead acetate, the cholesterol concentration increased from 131.5 ± 3.54 in the first week to 288 ± 5.19 mg Pb/dL on 28th day of the study. The serum protein concentration was also significantly (p<0.05) increased in the Pb – exposed groups when compared with the control group, it increased from 4.04 ± 0.06 mg Pb/dL on day 7 to 5.30 ± 0.05 mg/dL on day 28 in the fish exposed to 0.1 mg Pb/L. When the fish treated with 0.4 mg Pb/L, the serum protein increased from 4.45 ± 0.37 mg/dL on day 7 to 6.18 ± 0.19 mg Pb/dL on day 28, respectively. These changes are indicative of stress imposed on the fish by lead and could be used as indices of lead poisoning.