A Preble's meadow jumping mouse (Zapus hudsonius preblei) parasitized by five grey flesh fly (Wohlfahrtia vigil) larvae was discovered at the United States Air Force Academy in Colorado Springs, Colorado (USA), in June 1998. This is the first documented case of grey flesh fly parasitism of jumping mice (Family Dipodidae). The lesion was approximately 6 mm wide and was partially hidden under a mat of wet fur. Myiasis was found in one (0.7%) of 146 jumping mice captured at the Academy in 1998. The Preble's meadow jumping mouse is considered a threatened subspecies by the United States Fish and Wildlife Service. Although grey flesh fly myiasis can be fatal, it is unknown whether it is affecting populations of Preble's meadow jumping mouse. This is the first report of grey flesh fly myiasis in free-ranging wildlife in Colorado.