To advance the national early intervention agenda, priority must be assigned to the evaluation of services for families of infants and young children with developmental disabilities. This priority for evaluation rests on current considerations for accountability to families, accountability to funding sources, and the need for program documentation. Evaluation of ongoing interventions involving home- and center-based services for infants, toddlers, and their families, however, needs to focus on questions different from those for empirical research on early intervention efficacy. To this end, eight questions pertaining to the evaluation of clinical interventions can be viewed. Within the framework of an intervention cycle, referral, assessment, intervention planning, service implementation, and follow-up are discrete elements defining a sequence of encounters of children and families with service systems. This article illustrates the use of the intervention cycle as a framework for evaluation of clinical interventions and identifies representative measures and strategies appropriate for evaluation of each element of the cycle.