The purpose of this study was to investigate effects of time of day on physiological and physicalfitness factors in athletes and nonathletes. For consideration effect time of day ; tests to beperformed in crossing way at three times 7.00 - 9.00; 13.00 - 15.00 and 18.00 - 20.00 . finding:A significant diurnal variation was found for balance ; trunk strength ;power food ; bodytempreture and systolic and diastolic pressure. There was a significant different amongresponses of athletes and nonathletes to the effect of time of day on physical fitness factors justfor trunk strength. Hawever ; A significantmain matual effect of time of day and phases ofmenstruation cycle was observed for trunk strength. Conclusion: Other than the need to morresearchs ; result of this research showed that physiological and physical fitness factors ; aexcept balance has shown significant increase at afternoon.