Although negative surgical margins are an important prognostic factor in the breast-conserving treatment of breast cancer, the required width of these margins is still under debate. To define the risk of in-breast recurrence in subgroups of patients with a local high-risk situation, local control was evaluated in all patients with close or positive margins treated at one institution between 1995 and 2000. A total of 118 patients (67% T1, 30% T2, 52% N0) were identified as having had positive or close margins (< or =4 mm) at the time of initial surgery. Of these, 65% had no tumor cells at the initial margin, 35% had a positive or questionable margin. Re-excisions were performed in 42%. The median (range) whole-breast radiotherapy dose, tumor bed boost dose and total dose were 50 (46.8-56) Gy, 15 (8-20) Gy and 65.8 (54-71) Gy, respectively. Thirty-six percent received adjuvant chemotherapy. Local (in-breast) control was calculated by the Kaplan-Meier method and compared between subgroups. The 5-year local control for the whole group was 94%. The rates for selected subgroups were: <56 years 89.4% vs. >56 years 98.1% (p=0.073, univariate analysis); pT1 95.9% vs. pT2 88.6% (not significant, n.s.); pN0 96.6% vs. pN+ 90.8% (n.s.); initial margin free of tumor cells 95.5% vs. initial margin involved or questionable 90.7% (n.s.), no re-excision 96.7% vs. one or more re-excisions 90.6% (n.s.); adjuvant chemotherapy 81.7% vs. no adjuvant chemotherapy 100% (p=0.007). We conclude that among patients with close or positive margins, older patients achieved high local control rates with a median tumorbed boost to 66 Gy. Younger patients and patients who received adjuvant chemotherapy (due to the presence of histopathological risk factors) were at increased risk of in-breast recurrence and should be considered for intensified local treatment.