Multiresistant pathogens cause increasing problems in the therapy of nosocomial infections and post-surgical. A rational and restricted use of peri-operative antiinfective prophylaxis is recommended. In a prospective study in 260 patients who underwent surgery at the head and neck at the university hospital Mainz from July to Oktober 1998 the incidence and severity of post-surgical infections was analysed. Adequate microbiological procedures were performed. The diagnosis of an infection was defined clinically and was compared to the microbiologic findings. Laboratory findings were documented to identify systemic infections (eg. SIRS, Sepsis) from localised wound infections. In nearly all cases an antiinfective prophylaxis with a ß-lactam, cephalosporin or clindamycin was administered. 65 out of 260 patients (25%) showed clinical signs of infection. 12 of 260 (5%) were classified as nosocomial infections. Clinically documented infections: 1) Abszesses 50 of 50 (100%), 2) combined intra- and extraoral tumor resections 10 of 49 (20%) 3) dental surgical procedures 6 of 68 (9%), 4) non-contaminated extraoral procedures 1 of 15 (7%) 5) trauma patients 1/47 (2%) 6) malformations of the head and neck (cleft lip palate n=17, orthognatic surgery n=14) no infections. In only 50% of the patients with abszesses a pathogen was isolated, in the other groups the rate of microbiologically documented infections was above 80%. In all the groups nearly half of the isolated pathogens were Gram negative. The results show, that for certain surgical procedures of the head and neck (Trauma, orthodontic surgery, cleft lip palate) routine prophylaxis should not exceed a single dose administration. In contrast patients with risk factors (cancer patients) should receive a broad spectrum antiinfective prophylaxis to prevent nosocomial infections in this group. Keywords: digital dental radiography, CCD sensor, storage phosphor, dose reduction