This study was undertaken to investigate the effect of 2-week oral administration of a Lactobacillus-GG-fermented whey drink on fecal enzymes in elderly nursing home residents complaining of difficulties in defecation. The study was divided into three 2-week periods: baseline (2 dl placebo drink/day); Lactobacillus GG treatment (2 dl of a Lactobacillus-GG-fermented whey drink containing 10(8) cfu lactobacilli/ml); follow-up (2 dl placebo drink). Administration of the fermented whey drink resulted in colonization of feces by Lactobacillus GG in all the subjects. Glycocholic acid hydrolase activity and tryptic activity were significantly decreased at the end of the treatment period. The effect of Lactobacillus GG treatment on bowel function was less evident. Although the consistency of the stools appeared to normalize, no significant changes in the fecal frequency, weight and pH were observed. The results indicated that a Lactobacillus-GG-fermented whey drink can change the bacterial metabolism, and has no significant effect on bowel function.