We conducted a prospective randomized trial to compare the efficacy of oral gentamicin versus oral IgA‐IgG for the prophylaxis of necrotizing enterocolitis (NEC); 200 newborns considered at high risk for NEC were assigned to group A (oral IgA‐IgG, n= 100) or group B (oral Gentamicin, n= 100). NEC was diagnosed in 13 cases in group A and in 1 case in group B between the 3rd and 16th days of life. Surgical treatment was necessary in 3 cases (2 in group A). All infants survived. We conclude that oral gentamicin is more effective than oral IgA‐IgG in the prevention of NEC in infants at high risk.