A nosocomial infection is any infection of a healthy or an ill person that occurs independently of the primary illness. For that sort of infection it is necessary to determine whether it is a result of a diagnosis, treatment or medical care, whether it can develop during a medical treatment or care, after a diagnostic or therapeutic procedure and a hospital/a social welfare provider in a specific period of time. At a higher risk of attaining such an infection are children, elderly people, people with an impaired immune system, chronically ill patients and surgical patients. The cause of an infection can be almost any microorganism: bacteria, viruses, funghi and parasites. The most common hospital infections are urinary tract infections and the main risk factor for its occurrence is catheterisation. The catheterisation of the urinary bladder is a minor surgical procedure during which the urinary catheter is inserted into the bladder through the urethra in order to empty the bladder. The effects of catheterisation, i.e. urinary tract infection are the most common type of infection and therefore make up to 40% of all healthcare infections. The number of patients with urinary catheters is on the rise daily. Therefore, it is needed to perform the catheterization by standard recommendations and in a standard way, because even the slightest mistake leads to unwanted consequences that could even lead to a lethal end. The key of prevention is the education of patients with urinary catheters, so that they could know how to cope with difficulties in everyday life and thereby lower the risk of infections. In patients with urinary catheters, it is important to check the catheter and the drainage system, and document it daily. Excessive catheter handling should be avoided as this increases the risk of infection. A routine catheter change, catheter rinse and changing the drainage bag, as well as using antibiotics as a measure of prevention have shown inefficiency and are not recommended any more. The most effective prevention of urinary tract infections is to avoid inserting the urinary catheter, however if that is not possible, it is important to remove the catheter if any of the indications are no longer present.