Two studies assessed whether measures of health, well-being, and sleepiness are better related to sleep quality or sleep quantity. In both studies, subjects completed a 7-day sleep log followed by a battery of surveys pertaining to health, well-being, and sleepiness. In subjects sleeping an average of 7 hours a night, average sleep quality was better related to health, affect balance, satisfaction with life, and feelings of tension, depression, anger, fatigue, and confusion than average sleep quantity. In addition, average sleep quality was better related to sleepiness than sleep quantity. These results indicate that health care professionals should focus on sleep quality in addition to sleep quantity in their efforts to understand the role of sleep in daily life.