The ACDB was performed under the ambulatory portion of the Tri-Service Performance Measurement Study (PMS). The purpose of the PMS was to develop an alternative measure for military medical work units. Outpatient data collected in over 70 clinical specialties at six medical facilities over a 21-month period using optical mark sense technology is stored in central data base at Fort Detrick, Maryland. A total of 3,108,741 patient encounters were captured. Forth-four clinic encounter variables include diagnoses, procedures performed, time spent with patient, type of provider, and place of visit. Fourteen patient demographic variables and seven health care provider variables were also captured. Reliability of data was verified by a manual review of data collected against the medical record entries for 9,015 patient encounters at the six sites. Analysis of data will covered in subsequent reports. Keywords: Biomedical information systems, Records management, Optical scanning, Computers. (Aw).