After conservative treatment for breast cancer, 20% to 30% of patients have a residual deformity that sometimes requires surgical correction. Thirty-five of these patients were operated between 1990 and 1995 at the Institut Curie. The authors classify these sequelae into three types: type I, asymmetrical breasts with no deformity of the treated breast; type II, deformity of the treated breast, compatible with partial reconstruction and breast conservation; and type III, major deformity of the breast, requires mastectomy. Fourteen patients had a type I deformity; all but 1 patient were treated with maromaplasty. Seventy-one percent underwent unilateral surgery contralateral to the irradiated breast; 80% had a satisfactory cosmetic result (good or very good). Seventeen patients had a type II deformity. They were treated by various techniques (implant, mammaplasty, latissimus dorsi flap, or transverse rectus abdominis musculocutaneous flap). Only 43.8% of patients in this group had a late satisfactory cosmetic result. Four patients had a type III deformity. They were treated with mastectomy and immediate reconstruction using a musculocutaneous flap. All 4 patients had a very good cosmetic result. This classification is a valuable guide for technique selection. For type I deformities, surgery to the irradiated breast should be avoided when possible. Type II deformities raise the most difficult therapeutic problems. Because they are mainly postoperative, optimal treatment should be preventive—by performing immediate remodeling of the treated breast before radiotherapy. This pleads for integration of plastic surgical techniques at the time of the original lumpectomy, thus reducing the need for delayed reconstructive surgery.