FAP handles both the investigation and treatment of child and/or spouse maltreatment cases; thus it developed and implemented the United States Air Force (USAF) FAP’s Family Violence Severity Index (USAF-FAP). The USAF-FAP is used to quantify the severity of each type of maltreatment investigated by FAP (partner physical, emotional, and sexual abuse; child physical, emotional, and sexual abuse; and child neglect) using a multi-dimensional rating system. Although the USAF-FAP has been used to rate thousands of maltreatment cases worldwide, its reliability has never been investigated. Thus, the first study investigated the reliability of the USAF-FAP; 12 experienced USAF-FAP clinicians reviewed and made severity ratings on 184 archival FAP case records. Overall, findings indicated fair-to-good levels of interrater agreement, demonstrating the reliability of the instrument. The second study assessed interrater reliability using 21 standardized vignettes for the 12 clinicians to rate, rather than archival case records. The use of standardized vignettes allowed for the establishment of a “gold standard” against which to measure interrater reliability. Results of study 2 indicated that the overall reliability of the ratings was roughly equivalent when evaluated with standardized vignettes and with case records. Taken together, the results suggest that the USAF-FAP supports fair-to-good levels of reliability. The authors recommend continued work to refine the USAF-FAP so that reliability levels may be raised to excellent. However, the current reliability levels combined with face and content validity, are strong enough to recommend its use in civilian agencies looking for an easy maltreatment severity index. Tables, references, appendix