Sinus irrigation is the traditional treatment for chronic maxillary sinusitis. Functional endoscopic sinus surgery (FESS) restores aeration and allows secretions to be removed from an infected sinus. This study compares the efficacy of sinus irrigation with that of sinus irrigation followed by FESS in 89 patients. We measured the effects by way of sinus radiographs, nasendoscopic findings, and patient complaints. When we analyzed the data in terms of intent to treat, we found significantly favorable results for sinus irrigation followed by FESS at the end point, though only for loss of smell and purulent rhinitis. Treatment consisting of sinus irrigation alone prevented surgery in 58% of all patients for 1 year. Both treatment methods were combined with a 10-day course of loracarbef, which might have contributed to the outcome. We conclude that a good option for treatment of chronic maxillary sinusitis seems to be sinus irrigation in combination with a broad-spectrum antibiotic followed by FESS.