Some children experience persistent night-time fears that interfere with their daily functioning. Initially, we present developmental considerations necessary to an understanding of severe night-time fears. We postulate that severe night-time fears are probably due to a complex interaction of biological, environmental, and cognitive-mediational processes. Several assessment procedures are outlined: behavioral interviews, diagnostic interviews, fear survey schedules for children, home monitoring on the part of parents, and darkness toleration tests. Traditional behavioral interventions, and more recent cognitive-behavioral interventions, are evaluated in terms of their research foundations. Cognitive-behavioral strategies appear to have the more empirical support, although we draw attention to several methodological limitations.