Objective: This study assessed the relationship between the need for and use of mental health services among a nationally representative sample of children who were investigated by child welfare agencies after reported maltreatment. Method: Data were collected at study entry into the National Survey of Child and Adolescent Well-Being and were weighted to provide population estimates. Results: Nearly half (47.9%) of the youths aged 2 to 14 years (N = 3,803) with completed child welfare investigations had clinically significant emotional or behavioral problems. Youths with mental health need (defined by a clinical range score on the Child Behavior Checklist) were much more likely to receive mental health services than lower scoring youth; still, only one fourth of such youths received any specialty mental health care during the previous 12 months. Clinical need was related to receipt of mental health care across all age groups (odds ratio = 2.7-3.5). In addition, for young children (2-5 years), sexual abuse (versus neglect) increased access to mental health services. For latency-age youths, African-American race and living at home significantly reduced the likelihood of care. Adolescents living at home were also less likely to receive services, whereas having a parent with severe mental illness increased (odds ratio.= 2.4) the likelihood of service use. Conclusions: Routine screening for mental health need and increasing access to mental health professionals for further evaluation and treatment should be a priority for children early in their contact with the child welfare system. J. Am. Acad. Child Adolesc. Psychiatry, 2004; 43(8):960-970. Key Words: mental health services, child welfare, foster care, National Survey of Child and Adolescent Well-Being.