Toilet training is the mastery of skills necessary for urinating and defecating in a socially acceptable time and manner. In many cultures, parents regard the achievement of independent toileting as a significant accomplishment and a step toward self-sufficiency. Bladder and bowel function is regulated by complex muscles and may be modified by physiological, psychological, social, and cultural factors. Currently, an all-encompassing definition of "toilet trained" is lacking, and there are no strict criteria stating how long a child must be bladder or bowel continent, or what components of the toileting process a child must accomplish independently, in order to be considered "toilet trained." Over the last 100 years, recommended toilet training methods have oscillated between rigid programs and child-oriented ones. In 1962, Brazelton developed the "child readiness" approach, which focused on gradual training. This approach described parameters of child and parent toilet training readiness. The Azrin and Foxx method emerged in 1971 as a parent-oriented method that emphasized structured behavioral endpoint training aimed at eliciting a specific chain of independent events by teaching the component skills of toilet training. These two methods differ with respect to goal development, endpoints, and emphasis on the child's self-esteem. Other methods include variations of operant conditioning, assisted infant toilet training, and the Spock method. Some factors believed to impact toilet training include sex, age at initiation, race, physical or mental handicaps, and constipation. While the majority of children are toilet trained without incident, approximately 2 to 3 percent experience an adverse outcome. Common adverse events are enuresis, encopresis, stool toileting refusal, stool withholding, and hiding while defecating. Toilet training children with special needs presents a unique set of challenges as impaired communication skills, reduced ability to process sensory information, and mobility and neurophysiological deficits add challenges to their toilet training. Current published toilet training guidelines in North America recommend (1) a child-oriented approach, (2) not starting before 18 months because the child is not physically ready, and, (3) starting when the child displays interest. The American Academy of Pediatrics put forth the following four questions: 1. What is the evidence for effectiveness of various toilet training methods to achieve bowel and bladder control? 2. What factors modify the effectiveness of toilet training, such as age, sex, race, ethnicity, culture, age at initiation, constipation, or stool toileting refusal? 3. What is the evidence for various toilet training methods as a risk factor for adverse outcomes, such as dysfunctional voiding, enuresis, encopresis, later problems, and psychological consequences? 4. What is the effectiveness of toilet training methods for achieving bowel and bladder control among patients with special needs?