This is the second of two papers addressing the occupational behavior and sensory integration approaches to occupational therapy for children. In the previous paper, basic concepts from these two approaches were discussed as presenting different, yet complementary, perspectives. The use of play was identified as central to occupational therapy practice from either perspective. Concepts from both approaches were integrated into a general systems model of play development in infancy and early childhood. This paper discusses play and sensory integration as interdependent developmental phenomena that are a function of interactions between the environment (input) and the child’s internal processing (throughput). When input-throughput interactions do not permit the growth of competence, dysfunction occurs. Consideration of possible input and throughput deficits are suggested for assessment of individual children, and treatment guidelines are drawn from both the sensory integration and occupational behavior literature.