Individuals differ in their timing of sleep (e.g., bedtimes, rise times) and in their preference for morning or evening hours. Chronotype refers to these differences in morningness-eveningness. Adolescents become later chronotypes during puberty, and the transition occurs around the age of 12-14 years. The authors assessed this change among German adolescents using measurements for chronotype, pubertal development, and parental monitoring. Chronotype and sleep parameters correlated significantly with age, suggesting that older adolescents become more evening oriented, sleep less, and have later rise and bedtimes. The authors obtained similar results when assessing puberty scores. Parental setting of bedtimes during the week decreased with age, and it was nearly absent at the age of 17 years. Adolescents without parental monitoring went to bed later and were later chronotypes. Using linear regressions, the authors found that age was the only significant predictor of chronotype, whereas age, pubertal status, and parental monitoring significantly contributed to bedtime during the week and sleep length on weekdays.