Dr Nazari et al1 presented an excellent example of allergic fungal sinusitis in the "Radiology Quiz Case" section of the March issue of the ARCHIVES. Their listing of differential diagnoses is worthy of further discussion. The diagnosis of invasive fungal sinusitis solely by computed tomographic (CT) findings may be an oversimplification. The early stages of invasive fungal sinusitis cannot be differentiated from noninvasive sinusitis by CT only. On the contrary, a patient may have invasive fungal sinusitis well before bone erosion and tissue necrosis are visible on CT. In the absence of characteristic CT findings, the CT scans must be correlated with other clinical findings such as association of diabetes, prolonged steroid use, chemotherapy, or other immunosuppression before such a conclusion is tenable.