An ongoing randomized study of a specific regimen of hypofractionated radiation therapy (IHF) versus classical or standard radiation therapy (IC) for breast cancer was begun in the Department of Radiation Therapy of the Necker Hospital, Paris France, in January 1982. Breast cancer patients entered into this study received either IC to deliver 45 Gy in 25 fractions over 33 days or a specific IHF regimen to deliver 23 Gy in 4 fractions over 17 days. As of June 1989, 525 patients had been entered into the study. The first 230 patients treated from 1982 through December 1984 had a minimum follow-up of 4 years (range: 4 to 7 years). Preliminary analysis of the results in these first 230 patients are presented. The distribution of patients in this initial group according to clinical staging, associated treatments, and pathological nodes is as follows: T1 = 22%, T2 = 61%, T3 + T4 = 17%, palpable nodes = 28%, inflammatory signs = 7%, surgical treatment = 79% (mastectomy = 35%, tumorectomy + Ir.192 = 44%), radiation alone + neoadjuvant chemotherapy = 21%, N+ = 50% of patients undergoing surgery. Loco-regional recurrences developed in 7% (9/125) of patients in the IHF group and in 5% (5/105) of patients in the IC group. Complications were minor. The addition of the percentage of each complication noted results in a total of 23% for the IHF group and 19% for the IC group (one patient could present several complications). As we had previously observed when comparing these two fractionation regimens in other studies with other tumors, these preliminary results showed no evident difference in the effectiveness and rate of complications whether IHF or IC was used to treat patients with breast cancer.