516 urines of 258 persons urologically ill with and without infection of the urinary tract collected in routine work were comparatively examined. Only such patients were taken into consideration who did not undergo an antibiotic therapy or who had made a pause of at least 3 days in the antibiotic therapy. The collection of the urine was carried out by means of puncture of the bladder as well as according to the mid-stream principle or by means of catheterisation. The qualitative and quantitative diagnostics of germs did not result in a significantly increased exactness of the examined urines collected by puncture of the bladder compared with the catheter or mid-stream urines. Therefore, the collection of urine by means of puncture of the bladder should be reserved for aimed indications and should not be taken into routine work. The catheter and mid-stream method is further entitled as screening method. Above all the falsely positive results condition the inexactness of this method. But also the urines collected by puncture of the bladder showed contaminations which account for our critical estimation.