To determine the relation between breast self-examination and survival of breast cancer patients, the authors studied 1004 newly diagnosed invasive breast cancer patients in Vermont general hospitals from 1 July 1975 to 31 December 1982. More frequent breast self-examination was associated with a greater likelihood of the patient's detecting her own cancer, less delay from first symptom to histologic diagnosis, earlier clinical stage, smaller pathologic tumor size, and fewer axillary node metastases. At a median follow-up time of 52 months (maximum follow-up, 92 months), 14% of the breast self-examination performers had died of breast cancer versus 26% of the nonperformers (P less than 0.001 based on chi-square). The product limit survival curve for breast self-examination performers (N = 424) was significantly better (P less than 0.001 by log-rank test) than for breast self-examination nonperformers (N = 411). Survival at 5 years was 75% for breast self-examination performers versus 57% for the nonperformers. The significant survival differences persisted after adjusting for any combination of the covariates age, method of detection, family history of breast cancer, and delay in treatment (P less than 0.002). Lead-time would have to be at least 3 years to negate the apparent beneficial effects of breast self-examination on survival. The authors conclude that in this population of breast cancer patients, breast self-examination was related to earlier detection and improved survival.