In a direct comparison series between 400 midstream urinesamples and 400 suprapubic aspiration specimens, but as well in an indirect comparison series of the same number of catheter urine-samples, bacteriological examinations were executed by means of the culture method before and after gynaecological operations. 19,5% of the suprapubic aspirates, 20,5% of the catheter specimens, and 25,5% of the midstreamsamples showed a significant bacteriuria. The number of false positive findings was in regard of the midstream urinesamples more than a quarter of the total infection rate. In midstreamsamples, mixed infections were 3,4 times more frequent than in catheter specimens. After a discussion of the results under special consideration of the high number of findings needing control in connection with operative problems, a valuation of the obtaining of urine in the field of operative gynaecology is demonstrated.