The displacement of sports and other physical activities by television and video may contribute to the associations among television viewing, obesity, and reduced physical fitness. Because video games are widely played by children and adolescents, we assessed the metabolic and cardiovascular responses to video game playing. Heart rate, blood pressure, and oxygen consumption were measured serially over 30 minutes in 32 males and females aged 16 to 25 years (mean +/- SEM, 20 +/- 1 years) while they played the "Ms Pac-Man" video game under standard laboratory conditions and compared with measurements made in a standing but inactive position. Playing the video game significantly increased heart rate, systolic and diastolic blood pressure, and oxygen consumption. Energy expenditure increased from 6.08 +/- 0.24 kJ/min while the subjects stood inactive to 10.94 +/- 0.49 kJ/min while they played. The increase in metabolic rate and cardiovascular stimulation was similar in magnitude to mild-intensity exercise.