Urinary tract infections still are a diagnostic as well as a therapeutical problem. The knowledge on the frequency of the causative organisms and their sensitivity to antibiotics and the different modes of urinary tract infections as well are very important, especially because of remaining organizational and medical-technical problems to identify the organisms. E. coli-bacteria are up to now the most frequent pathogens of urinary tract infections, with a resistance rate of 30% against aminopenicillins. An increase of resistant Enterobacter- and Pseudomonas-aeruginosa-strains against quinolones is known and could be observed also in our hospital. The demand for knowledge of sensitivity pattern of the causative organisms still remain for a successful antibiotic therapy.