The Child and Adolescent Services Assessment (CASA) is a self- and parent-report instrument designed to assess the use of mental health services by children ages 8 years to 18 years. The CASA includes 31 settings covering inpatiem, outpatient, and informal services provided by a variety of child-serving providers and sectors. This instrument collects information on whether a service was ever used and more detailed information (length of stay/number of visits, focus of treatment) on services used in the recent past. A description of the instrument, information on interviewer training and coding of data, psychometric data on clinical samples, and a case study are presented.