Hyperthermic tumor response induced by 1,064-nm radiation from an Nd:YAG laser was investigated in DBA/2J female mice bearing the SMT-F mammary carcinoma. The measured temperature-depth profiles indicate that hyperthermic temperatures can be achieved in tumors ranging from 3 to 8 mm thick at power inputs on the order of 1 W. For small tumors, a 5-week complete response rate exceeding 50% required 45 minutes at 45.0 degrees C. Control of large tumors (6-8 mm thick) was not achieved. The observed tumor response rates are consistent with semiempirical time-temperature relations based on other heating modalities.