• Mineral trioxide aggregate (MTA) was assessed in pulpotomised primary molars.• The clinical and radiographic success rate of MTA was recorded at 24 months follow-up.• This clinical trial study showed the success of white MTA in primary molars. I N B R I E F RESEARCHPurpose The aim of this study was to compare the effect of white mineral trioxide aggregate (MTA) to that of formocresol (FC) as pulp dressing agents in pulpotomised primary molars. Methods In this clinical trial study, 60 lower second primary molars of 46 children were treated by a conventional pulpotomy technique. The teeth were randomly assigned to the MTA (experimental) and FC (control) groups by random numbered table. Following removal of the coronal pulp and haemostasis, 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. The teeth of both groups were restored with stainless steel crowns. Children arrived for clinical and radiographic follow-up evaluation after 6, 12 and 24 months. Results The treated teeth in FC group (n = 18) were clinically and radiographically successful after 24 months. The radiographic follow-up evaluation revealed one failure (furcation involvement) in 18 molars treated with MTA after 24 months. The treated teeth in MTA group were clinically successful 24 months postoperatively. Pulp canal obliteration was observed in one of the teeth treated with MTA and four of the teeth treated with FC. Conclusion MTA could be used as a safe medicament for pulpotomy in cariously exposed primary molars and could be a substitute for FC.