The endoscopic endonasal transsphenoidal approach (EEA) to treat sellar, parasellar, and suprasellar tumours continues to gain increased significance. Due to the close proximity of the sphenoid sinus to the carotid artery and the optic canal, it is very important for surgeons to know the anatomical features and variations of the sphenoid sinus as relevant to EEA. A prospective study of the sphenoid sinus morphology was carried out on the cranial tomographic (CT) scan images of 60 Nigerian adult patients. The CTs were reviewed regarding the different anatomical variations of the sphenoid sinus: dimensions, septation, and pattern of pneumatisation. There were 37 males and 23 females. The patients' ages ranged from 18 years to 85 years, with a mean of 47.2 years. There was a main single intersphenoid septum in most patients (95%). The insertion of the septum was usually to the right posteriorly (38%) and in the midline anterior (65%). Although there is usually a main septum, the septa present were multiple in 29 of the sinuses studied. There was no gender difference with respect to the attachment of the main sphenoid sinus septum. The sphenoid anterior, posterior, and transverse dimensions were not significantly dependent on age, but they were longer in males than in females. Sellar pneumatization was present in the majority of the patients (83%), with 4 patients having postsellar pneumatization (6.7%) and 3 patients having presellar pneumatization (5%). There were no cases with conchal pneumatization or lateral pneumatization of the greater wing of the sphenoid. The present study provides anatomical information about the sphenoid sinus dimensions morphology that is essential for avoiding complications in performing an endoscopic sphenoidotomy.