Sulfadiazine-related stones are uncommonly reported, but they could be increasingly encountered owing to the use of sulfadiazine for human immunodeficiency virus-related toxoplasmosis. We report on their unusual imaging characteristics, with 4 such stones having very low attenuation compared with more commonly encountered stones. Because their atypical appearance resulted in delayed treatment for our patient in acute renal failure and because the computed tomography imaging characteristics have not been previously defined, we report the findings of stone analysis-confirmed sulfadiazine-related urolithiasis.