This review provides an overview of an important aspect of early childhood home visiting research: understanding how parents are involved in program services and activities. Involvement is defined as the process of the parent connecting with and using the services of a program to the best of the client's and the program's ability. The term includes two broad dimensions: participation, or the quantity of intervention a family receives; and engagement, or the emotional quality of the family's interaction with the program. Research that includes examination of parent involvement is reviewed, including examples from the Early Head Start Research and Evaluation Project. Factors that influence involvement are noted, including parent characteristics, qualities of the home visitor, and program features. The need for further measurement development and implications of these findings for home visiting programs are discussed.