Phytohemagglutinin-P (25 and 50 mg/kg; i.p.; daily for 15 days; male Sprague-Dawley rats) shows a decrease in longitudinal bone growth, in the number of chondrocytes, in the thickness of cartilage plate, in the metaphyseal mass of hard tissue, in the percentage of calcified cartilage core, and in the number of osteoblasts per mm of bone surface. Additionally, PHA-P increases the number of osteoclasts, the number of labeled osteoclastic nuclei, and the average number of nuclei per osteoclast.