On and over a pole consisting of six stripes alternately white and maroon and extending diagonally from right to left, a gold fleur-de-lis above a scroll of the same, bearing the motto "AID TO THE WOUNDED" in maroon letters. The insignia is 1 3/32 inches (2.78 cm) in height.
The fleur-de-lis represents service in France during World War I and participation in the Meuse-Argonne Offensive. The striped pole is the ancient symbol of the surgeon; its colors are those of the Medical Department and the number of stripes produces the numerical designation of the former organization.
The distinctive unit insignia was originally approved for the 6th Surgical Hospital on 20 September 1941. It was redesignated for the 91st Evacuation Hospital (Motorized) on 15 October 1942. It was redesignated for the 91st Evacuation Hospital on 15 June 1968. The insignia was amended to change the motto and the symbolism on 1 November 1966.