The olfactory cleft is the specific site of development of many tumours (respiratory epithelial adenomatoid hamartoma, intestinal-type adenocarcinoma, neuroblastoma, inverted papilloma, glomangiopericytoma, etc.) and is also the site of CSF rhinorrhoea via the cribriform plate (cribri-rhinorrhoea). Olfactory cleft surgery must therefore be considered to be a specific type of surgery, complementary to ethmoidal labyrinth surgery and anterior skull base surgery. Olfactory cleft tumours can be resected according to five different surgical procedures: olfactory cleft mucosal resection, partial resection of the olfactory cleft, total resection of the olfactory cleft, unilateral endoscopic anterior skull base resection, and bilateral endoscopic anterior skull base resection. The diagnosis and closure of cribri-rhinorrhoea (i.e. documented CSF rhinorrhoea, demonstrated to arise from the cribriform plate during endoscopic examination of the olfactory cleft under general anaesthesia in a patient with no localizing signs on imaging) completes this range of treatment options.