Three-centimetre linear incisions were made in 90 young male Lew/f Mai rats by scalpel through skin to the investing fascia of the left flank. The skin was undermined sharply for a distance of 0.5 cm along both sides of the entire length of the incision. The wound site was closed per primam with Michel clips and left uncovered. Following emergence from anesthesia, rats were randomly allocated to one of three groups of 30 rats each: one group breathed air only and acted as control; the second was exposed to 20% N2O for 24 hours daily until sacrificed (continuous group); the third was exposed to 20% N2O for 8 hours daily until sacrificed (intermittent group). Ten rats from each of the three groups were sacrificed after 3, 7, or 10 days postincision. After sacrifice, sections from the wound stained with hematoxylin and eosin or reticulin were examined microscopically. No histological evidence of an effect on wound healing of skin occurred in rats exposed to 20% N2O.