In a prospective randomised study in hospitalised patients in the year 1973 and 1998 microbial findings in odontogenic abscesses and wound infections were recorded. In severe odontogenic abscesses the profile of bacteria changed: the "typical" Gram positive pathogens, which predominantly identified in 1973 were less frequently observed in the recent study episode. In contrast, the number of Gram negative bacteria appears to be increased in 1998. Additionally, the number of culture negative episodes in severe odontogenic abscesses seems to be increased. In the group of patients with post operative wound infections the number of Gram negative bacteria remains unchanged, accounting for >50% of the culture positive episodes. In the data from 1998, a high incidence of anaerobes is found in both groups of patients, emphasising the need for routine testing of these pathogens. Yeasts identified in both patient groups seem to have increased but their pathogenic role has to be further elucidated. Keywords: Rahmenlose Stereotaxie, computergestützte Chirurgie, Zygomaticus Fixture, Tumorchirurgie