This report describes options for study designs to evaluate the effect of early intervention on infants and toddlers, birth to three, with disabilities or developmental delays and their families in Washington state. Information was gathered from extensive literature reviews, a survey of local assessment efforts in Washington, a technical data inventory, and a consultation with stakeholders such as service providers, agency personnel, the Office of Superintendent of Public Instruction, parents, and community supporters. Recommendations include: (1) using a small- scale longitudinal study, retrospective cross-sectional study, or a key informant study for early intervention research; and (2) using an integrated research plan that logically and methodically addresses: who the children and families are who are receiving services, what are their needs, how services are addressing the needs of children and families, and what child and family outcomes occur as a result of service provision. Appendices include information on child and family characteristics, a local assessment survey, state and national early intervention goals, and possible statistical models for using subjects as their own control. (Contains over 150 references.) (CR)