The results of therapeutic pulpotomies in primary molars with farm-cresol technique were studied by systematic follow-up. Of 84 primary lower molars in the clinical study, 56 became available for histological examination. The radiographic follow-up revealed periradicular osteitis in 10 per cent of the teeth treated. Internal root resorption was seen in 37 per cent of the teeth, or one-fifth of the roots treated.The histological examination revealed a very capricious diffusion of the medicament throughout the pulp tissue. Vital pulp remnants in the apical part of the treated roots showed no signs of healing. All pulps presented a varying number of inflammatory cells in the border zone adjacent to the formocresol-fixed region. In 80 per cent of the roots the histological sections revealed signs of internal resorption with or without incomplete repair tissue formation.