The purpose of this study was to evaluate the effect of direct pulp capping using recombinant human BMP-2 (rhBMP-2) on dentin regeneration. RhBMP-2 (1.0 mg/ml) was dissolved in alginate-based gel (AG). Cavities with the exposed pulp area were prepared of first molars in Wister rats. All cavities were divided into two groups: The exposed pulps were covered with AG contained rhBMP-2 (BMP group), and covered with AG alone (AG group). Then they were sealed with glass ionomer cement (Fuji IILC EM). The animals were sacrificed at 3 and 8 weeks after operation. In both groups, the covered materials were observed at 3 weeks after operation, while they had disappeared and the tertiary dentin formation was observed into the prepared cavity at 8 weeks after operation. Thickness of the tertiary dentin of BMP group was significantly higher than that of AG group (P<0.05). These results suggest that AG is effective scaffold and direct pulp capping using AG contains rhBMP-2 is capable of enhancing dentin regeneration.