Acute graft-versus-host disease (GVHD) usually involves the skin, gastrointestinal tract, and liver. A 47-year-old woman with fever of unknown origin was referred for a Ga-67 scan. The study showed diffuse uptake of Ga-67 throughout the skin. Subsequently, a skin biopsy confirmed the diagnosis of acute GVHD. The incidence, diagnosis, and pathophysiology of the dermatitis in acute GVHD are discussed.