Acute gastric zygomycosis (mucormycosis) was diagnosed in four 6- to 7-day-old pigs with large venous infarcts in the gastric fundus. Two pigs were from one farm where several dams had developed fever at parturition and most of their litters had died. The other 2 pigs, from separate farms, had diarrhea that was unresponsive to broad-spectrum antibiotic therapy. Histologically there was severe hemorrhagic, ulcerative gastritis associated with numerous transmurally invading, mucoraceous fungi. The discussion includes speculation on the pathogenesis of this lesion in neonatal pigs.