We studied the cost-benefit of using probiotics (Lactobacillus acidophilus and Bifidobacterium bifidum) in the treatment of 106 children hospitalized with acute diarrhea using a double-blind randomized, placebo-controlled trial. The median length of hospital stay was significantly shorter in the probiotics group than in the controlled group (2 versus 3 days, p=0.049), but the median duration of diarrhea and direct medical costs were not significantly different (4 versus 5 days, p=0.068 and 4,418.75 versus 4,778.75 Thai Baht, p=0.342). Taking into consideration parental income loss, a non-significant lower expense was seen in the probiotics group (6,800.33 versus 7,970.92 Thai Baht, p=0.177). A greater cost-benefit with the probiotic treatment is probable, but was not statistically significant in this small study. In conclusion, the probiotics tested shortened the duration of hospitalization of children with diarrhea but the total expenses were not different.