DESCRIPTION (provided by applicant): We have pioneered the development of a prelinguistic and linguistic milieu intervention (PLMT) designed to establish intentional communication and enhance the development of early communication and language development in toddlers and young children with language delays and disorders. PLMT involves direct intervention with toddlers as well as parent training designed to establish and support a highly responsive style of parent-child interaction. Our preliminary research using randomized experimental design s has involved a very small "dose" of direct intervention with the child, averaging approximately one hour per week for six months. The effects we have observed have been encouraging, but moderate, especially when measured directly after the 6-month intervention period. The proposed research is a test of the hypothesis that more intensive application of PLMT will have dramatically more positive outcomes, We propose an experimental investigation of the effects of PLMT delivered at two different levels of intensity to 80 young children with general communication delays randomly assigned to either a "high" or "low" intensity group. Children in the low- intensity group will receive one hour of direct intervention per week for 9 months while children assigned to the high-intensity group will receive 5 hours a week of direct intervention for 9 months. All subjects in both groups will be followed for an additional 6 months. Specific aims of the study are to compare the effects of high and low doses of PLMT on children's nonverbal and verbal communication skills. We will also test hypothesized interactions between the interventions and several child pretreatment characteristics and test predicted mediators for the predicted treatment effects. Analyses will include t-tests, 2x2 ANOVA, and multi-level analysis (HLM). Multiple regression or ANCOVA will be used if statistical control of pre-treatment differences are necessary. Five years of funding is requested.