We compared different lactic acid bacteria for their effect on the immune response to rotavirus in children with acute rotavirus gastroenteritis. After initial oral rehydration, 49 children aged 6 to 35 months with rotavirus gastroenteritis randomly received either Lactobacillus casei subsp. casei strain GG (LGG), L. casei subsp. rhamnosus (Lactophilus), or a combination of Streptococcus thermophilus and L. delbrückii subsp. bulgaricus (Yalacta) twice daily for 5 days. Serum antibodies to rotavirus, total number of immunoglobulin-secreting cells (ISC), and specific antibody-secreting cells (sASC) to rotavirus were measured at the acute stage and at convalescence. The mean (SD) duration of diarrhea was 1.8 (0.8) days in children who received LGG, 2.8 (1.2) days in those receiving Lactophilus, and 2.6 (1.4) days in those receiving Yalacta (F = 3.3, p = 0.04). The ISC response was comparable in the three study groups, but the rotavirus-specific immune responses were different. LGG therapy was associated with an enhancement of IgA sASC to rotavirus and serum IgA antibody level at convalescent stage. We conclude that certain strains of lactic acid bacteria, particularly LGG, promote serum and intestinal immune responses to rotavirus, and thus may be important in establishing immunity against rotavirus reinfections.