To assess the cosmetic results in relation to treatment technique, we retrospectively reviewed the results for 1159 Stage I-II breast cancer patients treated with conservative surgery and radiotherapy between 1970-1985. All patients underwent gross excision followed by radiation therapy including an implant or electron beam boost. The total dose to the primary site was greater than or equal to 60 Gy. Because of technical modifications introduced over time after 1981, the population was divided arbitrarily into two cohorts: 504 patients treated through 1981 and 655 treated between 1982-1985. Median follow-up time for surviving patients in the two cohorts were 107 months and 67 months, respectively. Cosmetic outcome was evaluated by the examining physician and scored as excellent, good, fair or poor. Excellent results at 5 years were scored in 59% of early cohort patients and 74% of the latter cohort (p = 0.002). Acceptable results (either good or excellent) were seen in 84% and 94%, respectively (p = 0.02). In the latter cohort, the likelihood of achieving an excellent result, but not an acceptable result, was significantly related to the volume of resected breast tissue and the use of chemotherapy. The number of fields (three-field technique, provided that fields are precisely matched, compared to tangents only) and boost type (implant vs electrons) did not influence the cosmetic outcome. We conclude that our current technique using breast RT to 45-46 Gy and a boost to the primary site of 16-18 Gy is associated with a high likelihood of acceptable cosmetic results and that this likelihood is not diminished by the use of adjuvant chemotherapy, a large breast resection, the use of a third field, or boost type.