When behaviors are reinforced with a variable interval reinforcement schedule, reinforcement is available only after an unknown period of time. These types of reinforcement schedules are most useful for reinforcing slow and steady responding and for differentially reinforcing behaviors that are incompatible with some problematic behaviors. This review helps define variable interval reinforcement schedules, uses the example of a strategy to manage thumb-sucking behavior to illustrate the implementation of these schedules, and describes potential applications in school and clinical settings.