Premature infants are at risk for a devastating infection of the intestines due to the immaturity of their intestines and immune system. Probiotics are bacteria with healthful qualities that are taken by mouth to improve the number of healthy bacteria in the intestines. Probiotics have been shown in several studies outside the U.S. to decrease the risk of serious intestinal infection and in one small study to improve the rate of weight gain in premature infants. Prebiotics are food supplements that stimulate the growth of healthy bacteria and suppress the growth of unhealthy bacteria. Prebiotics have been shown to improve the numbers of healthy bacteria in the stool of premature babies. Our study is designed to compare two over the counter probiotic/prebiotic combinations to each other and to a control group. Infants less than 35 weeks with a birthweight of 750-2000 gm are eligible and must be enrolled in the study within the first week of life. The babies are randomly assigned to either a control group (no probiotic/prebiotic, just a placebo), a group which receives Culturelle (Lactobacillus rhamnosus GG plus fructo-oligosaccharide, ConAgra), or a group which receives ProBioPlus (three strains of Bifidobacteria plus Lactobacillus acidophilus plus fructo-oligosaccharide, UAS Laboratories). The babies receive the study product by mouth twice daily for 28 days or until discharge (whichever comes first). Weekly measurements (weight, length, head size) and stool cultures are performed. Clinical progress is closely monitored and any episodes of infection are recorded.