Chronic sinusitis is a common condition that is frequently refractory to medical and surgical intervention. It has not been well defined as to which patient subgroups benefit from surgical intervention and which do not. Our purpose is to determine whether the presence of certain inflammatory cell types is predictive of postoperative outcome in sinus surgery for chronic sinusitis. We performed a retrospective chart review of 75 patients who underwent endoscopic sinus surgery or polypectomy between 1994 and 1996. Of these patients, 15 met inclusion criteria for chronic sinusitis, asthma requiring inhaled steroids, and 1 year preoperative and postoperative management by the allergist or otolaryngologist at Northwestern Medical Faculty Foundation. Ten of these 15 patients had a complete set of data allowing immunohistochemical analysis. Sections of sinus tissue obtained at surgery were hematoxylin and eosin stained and evaluated for the presence of lymphocytes, plasma cells, eosinophils, and macrophages. Immunostains for T lymphocytes, B lymphocytes, and macrophages were performed also. The total number of antibiotic courses patients received were enumerated into 6-month blocks for 1 year preoperatively and 1 year postoperatively as markers of disease activity. Postoperatively, four patients improved, three patients worsened, and three patients remained unchanged, as defined by the number of antibiotic courses required 1 year postoperatively compared with 1 year preoperatively. We found no difference in the magnitude or specific type of inflammatory cells present at the time of surgery between the groups. However, when the difference between the preoperative versus postoperative antibiotic courses was compared between patients who improved versus patients who did not improve, the improved group required markedly fewer courses relative to the nonimproved group (p < 0.009). Neither total magnitude of inflammation nor specific inflammatory cell types correlated with surgical outcome in this group. The patients who did not improve postoperatively had a statistically significantly lower number of preoperative antibiotics than the patients who improved. These findings suggest that patients with less severe disease may be less likely to benefit from sinus surgery.