This study is the first prospective longitudinal and clinical investigation of homesickness in children. The moods of 329 boys ages 8–16 were assessed on a daily basis during either a 2- or 4-week period of separation from primary caregivers. Results supported 4 hypotheses: (1) homesickness was prevalent and varied in intensity. 83% of the boys reported some homesickness on at least 1 day during their stay, and 5.8% experienced severe depression and anxiety; (2) homesickness was experienced as a combination of depression and anxiety, particularly the former; (3) younger boys were at greater risk for homesickness than older boys; and (4) homesickness presented most often as internalizing behavior and was sometimes detectable to observers who knew the boys. 63% of the boys who self-reported moderate or high levels of homesickness were judged by observers to be homesick. Inconsistent with popular notions, the most homesick boys became progressively more homesick over the course of their separation, experiencing a significant drop in homesickness just before reuniting with parents. The phenomenology of homesickness is discussed, as are issues of simultaneous depression and anxiety in children.