Objective: The purpose of this study was to investigate the expression of transforming growth factor-B, TGF-B1 during odontoblast and ameloblast differentiation. Methods: The analysis was made on 5-um serial sections of the glutaraldehyde-fixed and paraffin-embedded mandibular first and second molars of a neonatal mouse. A specific and affinity-purified antibody to TGF-B1 and a digoxigenin-labeled cRNA probe were used. Results: The results showed that the TGF-B1 was expressed in a spatial and temporal pattern in dental tissues. The immunoreactivity of dental tissues for TGF-B1 was consistent with the expression of TGF-B1 mRNA revealed by in situ hybridization before dentin matrix formation. The TFG-B1 was evenly expressed in dental papilla and inner enamel epithelium. The expression of TGF-B1 was increased in the layer of odontoblsts and amelobasts and in the stratum intermedium with the formation of dentin matrix, where the staining was also observed. Conclusions: These findings suggest that TGF-B1 may have an important role in extracellular matrix formation and cytodifferentiation.