The aim of this study was to determine the acute effects of static and Proprioceptive Neuromuscular Facilitation (PNF) stretches on maximal oxygen consumption (VO2 max). Ten physically active men (mean ± SD, 23.80 ± 1.54 years, 70.60 ± 9.70 kg, 1.74.60 ± 5.23 m), who were healthy students volunteered to take part in the study. The participants were subjected to Static and PNF stretching exercises. After the interventions, the Bruce treadmill protocol was applied to measure VO2 max values. The expired gases were collected and analyzed continuously using the Cortex Metalyzer II. Analysis of variance showed significant main effects for interventions (F(2,18)=10.74, p<.05) on VO2 max. The main result of this study showed that both static and PNF stretching exercises improved VO2 max values.