OBJECTIVE: To assess the effect of a 4-month high-intensity interval training programme on cognitive functioning, cerebral oxygenation, central haemodynamic and cardiometabolic parameters and aerobic capacity in obese patients. METHODS: Cognitive functioning, cerebral oxygenation, central haemodynamic, cardiometabolic and exercise para-meters were measured before and after a 4-month high-intensity interval training programme in 6 obese patients (mean age 49 years (standard deviation 8), fat mass percentage 31 +/- 7%). RESULTS: Body composition (body mass, total and trunk fat mass, waist circumference) and fasting insulin were improved after the programme (p < 0.05). V. O2 and power output at ventilatory threshold and peak power output were improved after the programme (p < 0.05). Cognitive functioning, including short-term and verbal memory, attention and processing speed, was significantly improved after training (p < 0.05). Cerebral oxygen extraction was also improved after training (p < 0.05). CONCLUSION: These preliminary results indicate that a 4-month high-intensity interval training programme in obese patients improved both cognitive functioning and cere-bral oxygen extraction, in association with improved exercise capacity and body composition.