In this study 200 patients that are candidates for myringoplasty will be chosen and divided into two groups randomly. In group A 1gr sefazolin an hour before beginning of surgery and every 6 hours after surgery until 24 hours will be given to the patients and in visit of patients 1,2,4 and 8 weeks after surgery ,if no infection is seen, no antibiotics will be administered . in group B ,in addition to the mentioned protocol (1gr sefazolin an hour before beginning of surgery and every 6 hours after surgery until 24 hours and then), 500mg cephalexin capsule every 6 hours until 10 days will be given to the patients. Ear infections will be checked in first, second, forth and eighth week after surgery and results will be accumulated in checklists with all information of patients including age, sex, size of eardrum perforation (total, subtotal, half, lesser than half), duration of surgery, duration of dry ear before surgery (2 months, 2-6 months, 6-12 months, more than one year), tympanosclerosis, ear discharge, type and amount of used antibiotics.