Objective: The purpose of this study was to investigate the expression of transforming growth factor-β, TGF-β1 during odontobiast and amelobiast differentiation. Methods: The analysis was made on 5-μm sertal sections of the glutaraldehyde-fixed and paraffin-embeddded mandibular first and seond molars of a neonatal mouse. A spectific and affinity-purified anatibody to TGF-β1 was expressed in a spatial and temporal pattern in dental tissues. The immunoreactivity of dental tissties for TGF-β1 was consistent with the expression of TGF-β1 mRNA revealed by in situ hybidization before dentin matris in dental tissues. The immunoreactiviry of dental tissues for TGF-β1 was consistent with the expression of TGF-β1 was evenly expressed in dental papilla and inner enamel epithelium The expression of TGF-β1 was increased in the laver of odontoblasts and ameloblasts and in the stratum intermedium with the formation of dentin matix, where the staining was also observed. Conclusions: These findings suggest that TGF-β1 may have an important role in extracellular matrix formation and cytodifferenation. (CJDR 1998; 2: 17-21).