A retrospective study was conducted to determine if physicians in otolaryngology practice adhered to the clinical practice guideline for adult sinusitis that had been issued by the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) 3 years earlier. We analyzed data obtained from the charts of 90 adults who had presented to an otolaryngology outpatient department with a diagnosis of chronic rhinosinusitis (CRS), acute bacterial rhinosinusitis (ABRS), or acute viral rhinosinusitis (AVRS); there were 76 cases of CRS, 11 cases of ABRS, and 3 cases of AVRS. Our goal was to ascertain how closely the treating physician had adhered to the AAO-HNS recommendations with respect to diagnosis, treatment, and prevention of these diseases. The study group was made up of 10 otolaryngologists. We evaluated 7 clinical practice metrics for CRS, 7 metrics for ABRS, and 3 for AVRS. We found that individual physician adherence rates for cases of CRS ranged from 0 to 100%; average scores for the 7 metrics ranged from 4 to 88%. For cases of ABRS, adherence scores ranged from 0 to 100%; average scores for the 7 metrics ranged from 0 to 41%. For AVRS, the rate of adherence for all 3 metrics was 0%. This study revealed wide variations in adherence to the AAO-HNS guideline, but overall adherence was generally poor. Adherence appeared to be worse for the acute types of rhinosinusitis than for chronic rhinosinusitis. In view of these findings, a worksheet was developed that clinicians could use to improve compliance with the guidelines.