Findings from this population-based study in Los Angeles County, California, suggest that recently diagnosed tumors of the parotid gland are related to prior x-ray therapy for acne (relative risk = 2.6; 95% confidence interval = 1.07, 6.34). Responses to interviews with 408 patients with a parotid tumor were compared with responses of 408 neighborhood controls. Risk increased with an increase in the number of acne treatments, and the relative risk for 15 or more treatments was 8.0. Clinicians who are still using this form of therapy, as well as those clinicians who care for patients who received this treatment, should be aware of this additional risk associated with its use.