Smoke condensates generated from mucous membrane of the canine tongue irradiated with a CO2 laser showed mutagenicity on Salmonella typhimurium TA98 under metabolic activation with S9 mix. Strain TA100 was not so sensitive to the condensates with or without S9 mix. Smoke condensates from electrocauterization on the mucosa of the canine tongue also showed mutagenic activity on TA98 and TA100 with S9 mix. The revertant number per mg of the smoke condensates from laser irradiation was one-half that of the smoke condensates from electrocauterization (1623 and 3371) in TA98. The mutagenic potency observed was comparable to that of cigarette smoke. The amount of these smoke condensates from 1 g of tissue was equivalent to those from 3--6 cigarettes as to total mutagenicity.