Streptococcus mutans is an important species in oral microflora and its components have been found to stimulate production of cytokines in dental caries. The aim of this study was to evaluate TGF-β in patients with S. mutans. Seventy samples were selected during pulpectomy and investigated for the presence of TGF-β by ELISA. The results were analyzed by t-test (α = 0.05). The results showed higher mean concentrations of TGF-β in inflamed pulpal tissues in subjects with dental caries associated with S. mutans, compared with intact pulpal tissue samples; these higher means were statistically significant in all cases (P < 0.05). The results of this study suggested relations between the production of TGF-β in dental caries caused by S. mutans.