0.7 mg/kg VCR was administered intravenously to nine rats in three experimental groups. One hour after VCR injection the animals were injected with 3H-proline. The animals were sacrificed 1.5, 5 and 24 h after the VCR administration, and by comparison with nine control animals similarly injected with sodium chloride solution and 3H-proline, it was shown that VCR causes an early, intracellular retention of labeled proline in the odontoblasts, an abnormal intracellular distribution of labeled material and a generally decreased secretion of dentinal matrix from the odontoblasts in the maxillary incisors. The severity of the effects were shown to vary in different parts of the incisors.