A lateral fronto-ethmoidal approach simultaneously exposing the frontal sinus and the nasal fossae appears to be a necessity for the surgical treatment of fronto-ethmoidal pathology. It is possible to fashion an osteo-plastic flap in the fronto-naso-maxillary region. The technique of the approach is described. The operation leaves no ocular functional sequelae and the scar is minimal. Twenty one operations by fronto-nasal flap approach are described, 10 for benign tumours of the fronto-ethmoidal system and 11 with the aim of re-aerating the frontal sinus for cases of complicated or iatrogenic serious sinusitis. The results are studied. The indications of the fronto-nasal flap are described: In tumour pathology, this technique must be used for osteomas and mucoceles of the fronto-ethmoidal system as soon as the ethmoidal component reaches or goes beyond the middle ethmoid. If the fronto-ethmoidal lesion only involves the anterior ethmoid, it is then accessible via simple frontal flap. Inverted papillomas which require wide exposure should also be treated via this approach. In infectious pathology, the fronto-nasal flap offers the possibility, after eradication of fronto-ethmoidal lesions and calibration of the naso-frontal canal, of re-aeration of the frontal sinus which seems preferable to its exclusion. The possibility of re-aeration of the frontal sinus by an osteo-plastic procedure is progress in comparison with lost bone craniotomy procedures.