BACKGROUND/AIMS: Physical activity (PA) is associated with a reduced risk of colorectal cancer. Thus, we examined the colon transit time (CTT) according to the physical activity level (PAL) in Korean adults. METHODS: The study subjects were 49 adults: 24 males and 25 females. The subjects used an accelerometer for 7 consecutive days to measure the 1-week PAL. The subjects took a capsule containing 20 radio-opaque markers for 3 days. On the fourth day, a supine abdominal radiography was performed. According to the total activity count of all study subjects, the upper 25%, middle 50% and lower 25% were classified into the high (H), moderate (M) and low (L) physical activity (PA) groups, respectively. RESULTS: The total CTT was significantly longer in the female (25.8 hours) than in the male subjects (7.4 hours) (P = 0.002). In regard to difference on PAL, although there was no significant difference among the male subjects, the right CTT in the female subjects was significantly shorter in H group than in M group (P = 0.048), and the recto-sigmoid CTT was significantly shorter in H group than in L group (P = 0.023). Furthermore, there were significant differences in total CTT between L and M groups (P = 0.022), M and H groups (P = 0.026) and between L and H groups (P = 0.002). CONCLUSIONS: The female, but not male, subjects showed that moderate and high PAL assisted colon transit.