In this study, the influence of commercial probiotic, Lactobacillus spp., supplementation was investigated on growth parameters and digestive enzyme activities in gilthead sea bream, Sparus aurata, during larval development. All experiments were triplicated and designed in three different administrations of probiotic from 3 days after hatching (DAH) concurrently with starting of exogenous feeding. In the first group, probiotic was added to live food (rotifer and Artemia). In the second group, probiotic was supplemented directly to both live food and water. In the third group, probiotic was added directly to water. Also. no probiotic treatment was maintained in control group. Total bacterial counts among probiotic probiotic-supplemented groups were significantly different from total bacterial counts in controls in water and digestive tract of larvae (p<0.05). The mean of total bacterial counts in control was approximately 4x10(4)-fold increased from the experimental groups in the sea water (p<0.05). Besides, mean digestive enzyme activities of all probiotics treatment groups were significantly different (p<0.05) with that of the control. Except probiotic water supplementation group, in all treatments. the specific activities of pancreatic and intestinal enzymes were significantly higher (p<0.05) in larvae to which probiotic had been supplemented by live food and live food with water. Also, S. aurora larvae that had probiotic administered by live food with water demonstrated significant (p<0.05) increases in both survival (13-105% higher) and specific growth rate (29% higher) as compared to controls. As a result, supplementation of probiotic to directly tank water could not significantly increase growth parameters and digestive enzyme activities and therefore, administration of probiotics by this method would not be effective in terms of husbandry parameters and nutritional condition. (C) 2008 Published by Elsevier B.V.