This discussion article considers applied behavior analysis measurement, assessment, and treatment of sleep and sleep-related problems among infants, children, and youth who are typically developing and have neurodevelopmental disabilities. Measurement has concentrated on designing practitioner-implemented methods and improving fidelity of data recording through sleep-monitoring instrumentation. The emphasis of assessment is identifying antecedent and consequence variables that promote sleep and evoke and maintain sleep-related problems. Treatment research has evaluated several effective interventions for problems such as delayed sleeponset, night and early morning waking, bedtime resistance, and unwanted co-sleeping. Early and contemporary applied behavior analysis research is reviewed relative to function-based treatment formulation, intervention integrity, social validity, and research-to-practice translation.