Participation in the natural settings of home and community is one of four major goals for families receiving Part C early intervention services. While participation has been formally recognized as an important service-related outcome, there is a need to build knowledge about its key features to adequately apply the concept in practice. The need for descriptive evidence about participation is due to the limited capacity of currently available measures to provide information on this outcome for applied decision-making by families, practitioners, researchers, and policymakers. For this dissertation, two studies were conducted to elucidate key characteristics and correlates of participation in home and/or community activities among families receiving Part C services. The first study involved secondary analysis of data from 2,003 families who participated in the National Early Intervention Longitudinal Study (NEILS), conducted between 1997-2007. The objective of this study was to identify significant correlates of full and limited community participation among families transitioning out of Part C services. Two classification trees were developed which identified a small set of correlates related to managing child's behavior and informal (friends and family) and formal (early intervention, other agencies and services) support. The second study employed qualitative methods to examine similarities and differences in how parents described their child's participation across a broader array of activities and settings than was captured in the first study. Parents were asked to describe their child's participation in eight types of activities in the home or community setting. Patterns of variability were identified in terms of (a) parent expectations of participation, by setting (how often) and activity type (how helpful; how interactive); (b) child, family, and environmental factors perceived to impact participation, both general (preferences and personalities of parent and child; weather conditions) and setting-specific (supplies and information; space; schedule; social and professional support; policies); (c) general strategies for promoting participation (maintaining an identity apart from being a parent; managing task of parenting together; finding ways to involve child) with specific examples of each theme as pertaining to specific activities; and (d) expectations for future participation (from nothing to something; going to college, having a job, and having relationships).