Patients who have undergone "mantle" field irradiation for Hodgkin's disease may develop symptomatic muscle atrophy in the treatment portal. This complication has received only scant attention in the clinical literature and its pathologic substrate has not been elucidated. We report the finding of nemaline myopathy in the previously irradiated and atrophic trapezius muscle of such a patient. Biopsy of clinically uninvolved gracilis muscle outside of the radiation portal revealed normal histology and ultrastructure. We are unaware of previous reports documenting such a phenomenon, which suggests that nemaline myopathy may evolve as a radiation-related disorder.