The aim of this study is to determine if breast conservative treatment is justified for patients with a positive family history of breast cancer and to investigate whether they have a worse prognosis. We performed a prospective cohort study of breast cancer patients, treated with breast conservative treatment with radiotherapy at the Radiotherapy Department of the Medisch Spectrum Twente. Between 1984 and 1996, 1204 patients with T1 and T2 < or =3 cm were treated. Family history (FH) was recorded according to first degree relative (FDR). Treatment consisted of lumpectomy with axillary dissection followed by radiotherapy to the whole breast with a boost to the primary area. Adjuvant systemic therapy was given to patients with positive nodes. A positive FH was noted in 243 (20.5%) patients, of whom 208 (17.6%) had one FDR, and 35 (3.0%) > or =2 FDRs. The local recurrence rate was 4.1%, with similar rates for all groups. In young patients, < or =40 years, a significant relation between local recurrence and FH was found. The distant metastasis rate was 15.5%, with the lowest rate (5.7%) among patients with > or =2 FDRs. Patients with a positive FH had significantly more contralateral tumours. The 5-year corrected survival was 91.3%. Among patients with a positive FH, a 5-year corrected survival of 91% was observed and the survival 100% among patients with one and > or =2 FDR. Family history is not a contraindication for breast conservative treatment and is not associated with a worse prognosis. Family history is not a prognostic factor for local recurrence rate in patients older than 40 years.