Harvard University partnered with several Early Head Start (EHS)/Head Start programs in Boston and Lawrence, MA, to achieve two primary goals. First, project staff investigated the feasibility of combining parent and teacher reports of toddlers' vocabulary over time, with the ultimate goal of developing accurate, efficient means for EHS/Head Start staff to assess and monitor the vocabulary development of toddlers, particularly those from Spanish-speaking homes. Second, researchers focused analysis on developing a deeper understanding of language development and attrition in toddlers and preschoolers who are acquiring more than one language. Participants included a sample of approximately 75 toddlers from Spanish-speaking homes and a peer sample of approximately 45 toddlers from English-speaking homes. Children and families entered the study at child age 2, 2 1/2, or 3 years. Children were followed through their pre-kindergarten year of Head Start. Results informed development of an integrated system to identify appropriate reporter(s) and languages to be assessed, integrate reports from multiple reporters, and to display results over time.