AIM: To investigate the effect of a fermented milk containing Bifidobacterium lactis DN- 173010 and yogurt strains (BIO ) on adult women with constipation in Beijing. METHODS: A total of 135 adult females with constipation were randomly allocated to consume for 2 wk either 100 g of the test fermented milk or 100 g of an acidified milk containing non-living bacteria (control). Stool frequency, defecation condition scores, stool consistency and food intake were recorded at baseline and after 1 and 2 wk in an intention-to-treat population of 126 subjects. In parallel, safety evaluation parameters were performed. RESULTS: At baseline, no differences were found between groups. Following consumption of test product, stool frequency was significantly increased after 1 wk (3.5±1.5 vs 2.4±0.6, P < 0.01) and 2 wk (4.1±1.7 vs 2.4±0.6, P < 0.01), vs baseline. Similarly, after 1 and 2 wk, of test product consumption, defecation condition (1.1±0.9 vs 1.9±1.2, P < 0.01 and 0.8±1.0 vs 1.9±1.2, P < 0.01, respectively) and stool consistency (1.0±0.8 vs 1.5±1.1, P < 0.01 and 0.6±0.8 vs 1.5±1.1, P < 0.01, respectively) were significantly improved. Compared with the control group, stool frequency was also significantly increased (3.5±1.5 vs 2.5± 0.9, P