Introduction: Hiking at moderate altitude is a p opular physical outdoor acti vity in senior s ( Burtscher et al., 2001). Previous studies revealed that acute aerobic exercise can diminish postural control ( Donath et al., 2012) . It has been additionally observed that exposure to hypoxia le ads to alteration s of neuromuscular function (Cymerman et al., 2001 ). However, the effects of both altitude exposure and acute exercise on postural control have not been investigated . Thus, the present study aimed at investigating acute effects of moderate normobaric hypoxia on static and dynamic balance performance before and after a bout of 40 minutes light walking. Methods: Thirty -six healthy seniors ( age: 62 (SD: 4) y; BMI: 25.3 (4.7 ) kg/m² ; VO 2 at 85% HR max : 30.5 (8.2 ) mL/kg bodyweight ) were examined on three days. The first day was set to evaluat e the ventilatory threshold (VT 1 ). Therefore, a treadmill exercise test (Pepper protocol) up to 85% of predicted HR max was conducted. On day two or three, respectively, either a 40- minute treadmill walk under normobaric sea level or normobaric hypoxia conditions (2600m) at VT 1 was randomly performed. Balance performance (postural sway within 10 seconds) was assessed on a force plate during single limb -eyes opened (SLEO) and double limb- eyes closed (DLEC) stance before and after walking . Spatio -temporal gait characteristics were collected t wo times during the walking period ( at 5’and 35’) employing the Inclinometer -based RehaGait device. Results: Only t imes effects were found for selected s patio -temporal gait parameters ( Cadence: p<0.001, ηp²= 0 .29; stride time: p=0.007, ηp²=0.28; temporal gait variability: p=0.01, ηp²=0.16 ) but no significant difference were found by stride length, double support and spatial gait variability. Heart rate and Borg revealed a significant chan ge over time (p<0.001, ηp²= 0.42 and p<0.001, ηp²= 0.46). A moderate time x condition effect was only observed for postural sway during single leg standing with opened eyes ( p=0.04, ηp²=0.11 ) . Discussion : A deterioration of cadence, stride time, temporal ga it variability was found . This finding might be attributed to fatigue -induced changes of temporal adjustments of gait patterns. Moderate altitude did not additionally affect gait. Interestingly, altitude revealed additional deteriorations of postural sway during single limb standing. Thus, we assume that severe postural tasks that require central adjustments might sensitively respond to moderate exposure to altitude.