Pulpotomies were performed on rhesus monkeys with use of formocresol to determine if there was uptake of 14C-formaldehyde into the systemic circulation after formocresol pulpotomies. Five-minute exposure of pulpal tissue to the 14C-formocresol resulted in the systemic absorption of approximately 1% of the dose. Two hours of exposure of pulp tissue to the 14C-formocresol did not increase the systemic absorption. Multiple sequential pulpotomies resulted in proportionately higher systemic absorption of 14C-formaldehyde. Application of 131I to pulpotomy sites indicated that formocresol compromises the microcirculation of the dental pulp. Autoradiography disclosed extensive concentrations of 14C-formaldehyde in the pulp, dentin, periodontal ligament, and bone.