The "living high-training low" model (LHTL), i.e., training in normoxia but sleeping/living in hypoxia, is designed to improve the athletes performance. However, LHTL efficacy still remains controversial and also little is known about the duration of its potential benefit. This study tested whether LHTL enhances aerobic performance in athletes, and if any positive effect may last for up to 2 weeks after LHTL intervention. Eighteen swimmers trained for 13 days at 1,200 m while sleeping/living at 1,200 m in ambient air (control, n=9) or in hypoxic rooms (LHTL, n=9, 5 days at simulated altitude of 2,500 m followed by 8 days at simulated altitude of 3,000 m, 16 h day(-1)). Measures were done before 1-2 days (POST-1) and 2 weeks after intervention (POST-15). Aerobic performance was assessed from two swimming trials, exploring .VO(2max) and endurance performance (2,000-m time trial), respectively. Reticulocyte, serum EPO and soluble transferrin receptor responses were not altered by LHTL, whereas reticulocytes decreased in controls. In POST-1 (vs. before): red blood cell volume increased in LHTL only (+8.5%, P=0.03), .VO(2max) tended to increase more in LHTL (+8.1%, P=0.09) than in controls (+2.5%, P=0.21) without any difference between groups (P=0.42) and 2,000-m performance was unchanged with LHTL. In POST-15, both performance and hematological parameters were similar to initial levels. Our results indicate that LHTL may stimulate red cell production, without any concurrent amelioration of aerobic performance. The absence of any prolonged benefit after LHTL suggests that this LHTL model cannot be recommended for long-term purposes.