The purpose of this retrospective study was to evaluate the survival of dental implants placed during ablative surgery in the interforaminal region of the original edentulous mandible in patients with squamous cell carcinoma of the oral cavity in relation to postoperative radiotherapy. Forty-eight patients treated in 1996-2003 with surgery alone or in combination with postoperative radiotherapy were analysed. In all patients, 2 to 4 Brånemark Mk II/III 2-phase implants were placed during tumour resection. A total of 139 implants were placed of which 61 (21 patients) received postoperative radiotherapy: 60-68 Gy as a boost dose on the primary tumour site and 10-68 Gy on the symphyseal area. No difference was found in percentage of functional dentures on implants between the radiated and non-radiated groups. The success rate of osseointegration was 97% in the postoperative irradiated group and 100% in the non-irradiated group. The prosthetic success rate (75%) was lower because in 12 of the 48 patients (34 implants) a functional denture could not be fitted due to tumour recurrence or metastasis (7 patients, 22 implants) or for psychological reasons (4 patients, 12 implants), independent of whether radiotherapy was administered. Postoperative radiotherapy does not affect the osseointegration of dental implants placed during tumour ablation and the ultimate number of functional dentures. Primary implant placement in edentulous mandibles may have advantages over secondary implant placement in patients with oral squamous cell carcinoma.