B BACKGROUND Adolescents is one of the community groups who have quantity of sleep hoursless than it should be. National Sleep Foundation estimates that approximately87% adolescents do not get enough sleep. Less hours of sleep quantity can affectthe cardiovascular function or physical fitness. Only a few studies about thecorrelation between quantity of sleep hours and physical fitness in Indonesia. METHODS A cross-sectional study was conducted using Chi-square test. This study wasperformed to 91 students in Labschool Jakarta Senior High School. Quantity ofsleep hours is measured by filling out the form and fitness measurements performed by standard tests fitness Rockport. The relationship between quantityof sleep hours and physical fitness was statistically analyzed with Chi-square test. RESULTS Respondents consist of 44 boys (48.35%) and 47 girls (51.65%), between the age15-17 years were studied in November 2014. There were 16 students (17.58%)with the quantity of sleep hours ≤5 hours and there were 75 students with thequantity of sleep hours >5 hours. There is a significant relationship between quantity of sleep hours and physical fitness (p=0.000). There is no relationship between physical fitness, quantity of sleep hours, and gender. CONCLUSIONS Students group with quantity of sleep hours >5 hours have a higher level ofphysical fitness, compared with students group with quantity of sleep hours ≤5hours.