This investigation used a new experimental model to apply pure coronal plane angular acceleration to a rodent, inducing concussion (mild traumatic brain injury). A mass was propelled down a drop tube toward the laterally extended moment arm of a rodent helmet fixture. Upon impact, the rodent helmet-head complex experienced mean angular acceleration of 368 krad/s2 (standard deviation = 30). All 26 specimens demonstrated a period of transient unconsciousness, mild ventriculomegaly, and absence of severe pathology. Injuries were classified as concussion based on scaled biomechanics, transient unconsciousness, macroscopic damage and minimal histological abnormalities.