Applied Behavior Analysis or ABA is the application of the empirically validated principles of behavior to build skills through directed instruction. ABA also seeks to treat problem behaviors by determining their function and arranging for intervention that teaches functional alternatives. ABA is an approach to analyzing each individual’s skill deficits and problem behaviors. Each child brings with them a distinct set of skills and deficits. No single treatment package can be used for all children and ABA is a method for examining the needs of each individual. Specific instruction can then be tailored to a child’s unique situation. ABA, for the treatment of autism, is the application of the principles of learning to 1) build skills and 2) treat problem behavior. It works because each person’s behavior is assessed to determine what skills they have not mastered and what types of problem behavior interfere with learning and social functioning. The assessment is then used to identify goals and progress evaluation methods.