The effects of outdoor exercise on urinary excretion of the 17-hydroxycorticosteroids (17-OHCS), catecholamine rhythm, and sleep-wake patterns in cockpit crewmembers were investigated before, during and after jet travel between Tokyo and Los Angeles (8-h time difference). On the day following arrival at Los Angeles (day 3) 5 crewmembers exercised outdoors for about 5 h (exercise group, aged 47.2 +/- 6.8 yr), and 5 others volunteered to remain in their rooms and go shopping after the flight (control group, aged 47.4 +/- 1.5 yr). The timing of the acrophase of the 17-OHCS rhythm and sleep-wake patterns showed similar patterns of advance in the two groups on the day of arrival in Los Angeles (day 2) compared with that at baseline (B) in Tokyo. In the exercise group, the acrophase of the 17-OHCS rhythm tended to be delayed on day 3, and then phase-advanced on the day following outdoor exercise (day 4). The timing of acrophase of the 17-OHCS rhythm and sleep-wake patterns showed gradual delay on days 3-4 in the control group, and a significant difference (p < 0.01) was observed between the groups for the acrophase of 17-OHCS rhythm on day 4. These results suggest that outdoor exercise has some effects in hastening the resynchronization to a new environment of the circadian rhythm of the urinary 17-OHCS excretion.