The assessment and treatment of self-injurious behavior (SIB) has received much attention in the literature; however, few studies have focused on early intervention for this behavior. In the current study, functional analyses with developmentally appropriate modifications were conducted in an outpatient clinic with 30 children (aged 10 months to 4 years 11 months) to assess SIB and problem behavior in its early stages. The reported mean age of SIB onset was 17 months, and head banging was the most prevalent topography. Functional analyses identified sources of reinforcement for SIB in 62.1% of cases; with the inclusion of all forms of problem behavior, sources of reinforcement were identified for 87.5% of cases. Function-based treatments were developed for 24 cases, with functional communication training prescribed most often (70.8% of cases). Implications of these findings for the development of early intervention programs for SIB are discussed.