Grape pomace is a natural product rich in dietary fiber and polyphenols. A major part of dietary polyphenols is not absorbed in the small intestine and can interact with colonic microbiota. The influence of grape polyphenols on Lactobacillus acidophilus CECT 903 growth was investigated through agar diffusion assays and cultures in liquid media. Grape phenolic extracts and some standards of phenolic compounds (caffeic acid, gallic acid, tannic acid, catechin, epicatechin, and quercetin) were assayed. All phenolic compounds tested did not exert an inhibitory effect on L. acidophilus growth at a maximum concentration of 5000 microg/disk in agar diffusion assays. In addition, a stimulatory trend in bacterial growth was observed in both grape phenolic extracts and tannic acid. The major finding was that grape pomace phenolic extract (1mg/mL) induced a significant biomass increase of L. acidophilus grown in liquid culture media. Further research into the interaction between phenolic compounds and other intestinal bacteria, as well as healthy consequences, is required.