Back mice are subcutaneous fibroadenomatous nodules that cause low back symptoms. Previous case reports do not provide systematic descriptions of the clinical presentation or long-term follow-up of this problem. This retrospective case series reports syndrome characteristics and treatment outcomes for injection therapy for "back mice." We completed telephone interviews, chart reviews, and written questionnaires for a convenience sample of 35 participants. Participants reported the following symptoms: pain radiating to the lower leg (37%), leg numbness or paresthesias (14%), and a median of 8 weeks of pain before treatment (range 3 weeks to 10 years). Thirty-one participants (89%) received lasting relief from injection of local anesthetic and corticosteroid. Injection therapy relieved both local and radiating symptoms but often did not eliminate the nodules. Thirty participants (86%) were "satisfied" or "very satisfied" with the treatment. There were no adverse events reported. Back mice can cause radiating pain that can be confused with other low back or leg syndromes. Injection treatment seems to be effective, long lasting, and well tolerated. Physicians should search for these nodules in patients with unexplained low back pain and try injection therapy before initiating expensive therapy.