Over the past decades, instruments and techniques of the transsphenoidal approach have greatly improved. All of these procedures, whether microscopic or endoscopic, have to pass through the sphenoid sinus to reach lesions. The sphenoid sinus is surrounded by several vital anatomical structures. Knowing the details of the anatomy of the sphenoid sinus can guide the surgeon through difficult corners of this approach. To study anatomic Variation of Sphenoid Sinus and Related Structures. We studied 200 CT examinations of the paranasal sinuses at Saraswathi Institute of Medical Sciences, hapur, U.P. The age range was 18 to 70 years with mean age of 43.56 years of which 128 (64%) were males and 72 (36%) were females. The commonest pattern of intra-sphenoid sinus septation was the presence of single and complete septation (72%), followed by the presence of Double septa (one complete and the other incomplete) n (8%). Single and incomplete were seen in 6% of subjects. Absent intra-sphenoid sinus septation was seen in 7%. The most common pattern of attachment of intra-sphenoid sinus septation is sellar type followed by left ICA type with attachment to the optic canal and lateral wall being the least common.