Midocean fronts have by now been well documented in the World Ocean. In view of this, a general circulation theory that admits interior fronts is considered in this paper and a new class of frontal solutions is discussed. The present solutions are distinguished by having fronts that originate at locations within the interior of the circulation. The locations of the front origins do not depend upon local effects; rather, they are set by conditions far from the front. Such fronts are thus referred to as “spontaneous shocks.” They occur in adiabatic wind-driven models, and participate in the ventilated thermocline. Indeed, calculating basin conditions that result in spontaneous shocks is a central objective of this paper. Aspects of some observed fronts also have counterparts in the theory, and it is suggested that spontaneous shocks in the ventilated thermocline resemble certain North Pacific observations.