Although puberty is a universal developmental process and the developmental sequence of pubertal changes tends to be similar for boys and girls, there are considerable individual differences in the timing of puberty. In this article, we reviewed well-cited empirical studies concerning pubertal timing and its developmental significance for mental health and social adjustment outcomes in adolescence. We present the major theoretical models about pubertal development and attend to the questions of why, when, and under what circumstances puberty is consequential. We draw conclusions and discuss implications for interventions and future research.