Data on the long-term effectiveness of behavioral treatment for self-injurious behavior in individuals with mental retardation is rare. We present 4-year follow-up data on a 28-year-old man whose severe self-injurious behavior was treated with brief contingent electric stimulation via the Self-Injurious Behavior Inhibiting System (SIBIS). Event data collected throughout follow-up showed reductions in head-hitting and head-banging from over 2,600 responses per hour to approximately 1 response per hour during much of the first 31 months of treatment. However, the rate of head-banging began increasing thereafter, with the SIBIS losing its effectiveness to such an extent that it was no longer clinically useful.