The effects of antibiotics after endoscopic sinus surgery (ESS) were investigated in a prospective, randomized, double blind, placebo controlled study in 202 patients. Hundred and one patients received cefuroxime axetil (Zinnat, 2 x 250 mg/d). The other half received placebo. Patients received no nasal packing and were treated with nasal washes and steroids. Ten subjective symptoms (headache, maxillary pressure, nasal obstruction, nasal secretions, blood, post nasal drip, sneezing, cough, smell disturbances and illness) were recorded daily and at weekly postoperative visits (including suction cleaning when indicated) seven endoscopic parameters were evaluated. There were no statistical differences in the total and individual symptom and endoscopic scores. There was no significant difference in the incidence of postoperative infections between both groups. In conclusion, antibiotics do not influence the immediate postoperative clinical evolution after ESS.