The computed tomographic scans obtained in a series of 800 patients referred for evaluation for functional endoscopic sinus surgery were examined to determine the prevalence and significance of anatomic variants. Fifty-two normal variants were identified within two major groupings of primary bony abnormalities and sinus air cell extensions. Although 743 (93%) patients had one or more variants, the nature of the variants in many instances was such that 325 (41%) patients could be considered "endoscopically" normal. Among the remaining cases, variations of the septum and middle turbinates, with or without anterior ethmoid sinus extensions, were found, usually in recognizable combinations, that could produce significant obstruction of the drainage pathways. However, where such obstructive patterns existed, an equal prevalence of patients with and without sinus disease was found in the presence of the same variant combination. Thus, the presence of anatomic variations, singly or in combination, does not represent a disease state per se.