The objective of this presentation is to understand the prevalence of co-occurring mental disorders as determined by a DSM-IV criteria–based approach to disorder ascertainment among a K-12 sample of children, drawn from a single school district in each of 4 states: Colorado, Florida, Ohio, and South Carolina. This study used data from the Project to Learn About Youth – Mental Health (PLAY-MH), which utilized a 2-stage design. First, teachers completed screening tools to classify a child as high vs low risk for externalizing, internalizing, or tic disorders. Parents of children who were selected into stage 2 participated in one-on-one interviews, including the Diagnostic Interview Schedule for Children, version IV (DISC-IV) to identify those who met criteria for one or more disorders. Analyses were restricted to 305 children with at least 1 disorder and used SAS v9.4 survey procedures (SAS Institute, Inc.; Cary, NC) to account for the complex sample design and produce weighted percentages and 95% CI; comparisons with nonoverlapping CIs are described as being different. Co-occurring disorders were present in over half of children with each disorder examined (51.7%, CI 40.0-63.3 for disruptive behavior disorders; 54.5%, CI 41.4-67.6 for ADHD; 58.4%, CI 43.9-72.8 for anxiety disorders; 90.3%, CI 80.3-100 for depressive disorders). Among children with an anxiety disorder, boys were more likely than girls to have a disruptive behavior disorder, children aged 5 to 11 years were more likely than children older than 12 years to have ADHD, and non-Hispanic White children were more likely than Hispanic children or children of another race/ethnicity (not including Black) to have a disruptive behavior disorder. Among children with a disruptive behavior disorder, non-Hispanic White children were more likely than Hispanic children or children of another race/ethnicity (not including Black) to also have an anxiety disorder. Mental disorder co-occurrence in the PLAY-MH sample is prevalent, particularly among children with a depressive disorder, with unique patterns of co-occurrence by disorder type and clinical and demographic characteristics. These results can be used in conjunction with other modes of mental disorder surveillance to inform mental health screening, treatment, and educational services.