Radiocolloid internal mammary lymphoscintigrams were carried out in 249 women who had undergone partial mastectomy. Only 39 patients, or 15%, had axillary sampling; of these, 19 were positive. At last follow-up, a minimum of two years from the date of study, the overall recurrence rate was 67% for patients with an abnormal lymphoscintigram and 34% for those with a normal lymphoscintigram. Actuarial survival rates projected to five years indicate a statistically significant difference in the prognostic implications of the normal and abnormal internal mammary lymphoscintigram, with 83 and 59% survival rates, respectively.