OBJECTIVE The aim of this study was to compare the effect of mineral trioxide aggregate (MTA) to that of formocresol (FC) as pulp dressing agents in pulpotomized primary molars with carious pulp exposure. METHODS Forty-five primary molars of 26 children were treated by a conventional pulpotomy technique. The teeth were randomly assigned to the MTA (experimental) or FC (control) group by a toss of a coin. Following removal of the coronal pulp and hemostasis the pulp stumps were covered with an MTA paste in the experimental group. In the control group, FC was placed with a cotton pellet over the pulp stumps for 5 minutes and removed; the pulp stumps were then covered by zinc oxide-eugenol (ZOE) paste. The teeth of both groups were restored with stainless steel crowns. Eighteen children with 32 teeth arrived for clinical and radiographic follow-up evaluation ranging from 6 to 30 months. RESULTS The follow-up evaluations revealed only one failure (internal resorption detected at a 17 months postoperative evaluation) in a molar treated with formocresol. None of the MTA-treated teeth showed any clinical or radiographic pathology. Pulp canal obliteration was observed in 9 of 32 (28%) evaluated molars. This finding was detected in 2 out of the 15 teeth treated with FC (13%) and in 7 out of the 17 treated with MTA (41%). CONCLUSIONS MTA showed clinical and radiographic success as a dressing material following pulpotomy in primary teeth and seems to be a suitable replacement for formocresol in primary teeth.