The Composite Health Care System (CHCS) is a medical informatics system designed by Science Applications International Corporation (SAIC) and used by all United States and OCONUS military health care centers. In 1988, SAIC won a competition for the original $1.02 billion contract to design, develop, and implement CHCS. Components and characteristics CHCS is module based: modules include RAD (radiology), LAB (Laboratory), PHR (Pharmacy), PAS (Patient Appointing & Scheduling), MCP (Managed Care Program; used to support TRICARE enrollees by enrolling them to Primary Care Managers), PAD (Patient Administration): MRT (Medical Records Tracking), MSA (Medical Service Accounting) medical billing, WAM (Workload Assignment Module), DTS (Dietetics), CLN (CLinical: Nursing, Physician, and Allied Health), DAA (Database Administration), ADM (Ambulatory Data Module) Medical Coding of outpatient visits, and TOOLS (FileMan). Currently all appointments are booked in CHCS, except for Walk-Ins and Telephone Consults, which can now be booked in AHLTA. CHCS is a text based BBS/ANSI like display accessed via DEC VT320 terminal emulation. CHCS supports outpatient Order Entry (LAB, RAD, PHR, Consults (ancillary procedures), one-time and scheduled/multiple appointment consults. CHCS can also support Inpatient charting and Order Entry with multi-paging with a page for each ward the patient is transferred, but this feature is not fielded/enabled at many medical centers. Instead Clinicomp's Essentris product is deployed at all MHS hospitals and has replaced the use of CHCS Inpatient module for nurse charting. An interface solution to allow Essentris Orders to be transferred into CHCS order entry is being deployed. AHLTA Armed Forces Health Longitudinal Technology Application (commonly referred to as AHLTA) is the clinical documentation engine for the Physicians to write their notes, put in orders, document procedures performed and provide the basis of medical coding information. This information is then sent into CHCS and its subsystems (ADM - ambulatory data module) provide the official repository of the medical coding information and handle the transmission of those encounters via the Comprehensive Ambulatory Patient Encounter Record (CAPER) interface. The clinical data is brought into the M2 DataMart for use in research, operational metrics, trend analysis, and many other business intelligence processes/products. AHLTA information is also contained in a Central Data Repository (CDR). This CDR contains information from AHLTA, CHCS, and AHLTA-Theater. The AHLTA CDR is a comprehensive full scale world-wide EHR repository. CHCS shares its original codebase with the VA's VistA system. Since its inception it has been customized for supporting the Military and their