Day-old broiler chicks were fed a Ca-deficient diet for 30 days. Gross, microscopic and radiographic examinations of the proximal tibiotarsus were done at 2, 3 and 4 wk of age. In 2 wk old chicks, the growth plate proliferating prehypertrophied zone (P-PHZ) was variably lengthened and disorganized, cartilage columns of the degenerating hypertrophied zone and metaphyseal primary spongiosa were shortened, and bone spicules of the secondary spongiosa were bordered by increased osteoid. In 3 wk old chicks, lesions were either similar or more pronounced, with the additional finding of metaphyseal peritrabecular fibrosis. In 4 wk old chicks, the P-PHZ decreased in length, osteoid seams and fibrous connective tissue were less prominent and tibial dyschondroplasia-like lesions were present. Dietary Ca-deficiency apparently produced rachitic lesions. The lesions were very different from those of P deficiency or Ca excess, and were variable over time.