Supplementing a practical chick starter diet with 30 mg tetramethylthiuram disulfide per kg of diet produced tibial dyschondroplasia (TD) in single-comb white leghorn chicks without compromising growth or bone mineralization. The incidence and severity of the lesion increased over time, with the highest incidence (40%) occurring in 4-week-old chickens. Microscopically, the lesion was consistent with the description of TD in broilers. This is the first known report of TD in the layer-type chick, which heretofore was felt to be highly resistant to TD.