There is a relationship between iatrogenic complications of medical procedures and the quality of medical services. The risk of iatrogenic complications or diseases occurring is growing over time for several reasons: patients under medical care grow older and sicker, diagnostic and therapeutic procedures are expanding at a fast pace, and complexity and uncertainty in daily care tends to grow. This development will continue unless we actively start to prevent iatrogenic complications. The frequency of iatrogenic illness was found to be between 4 and 36% of all patients treated in a hospital setting. The wide span is a result of different definitions of what is an iatrogenic complication. When an iatrogenic illness occurs we are obliged to look for "errors in the system"in order to eliminate them. In a hospital and practice environment the respective methods are different. By eliminating unnecessary procedures the risk of possible damage is diminished. Necessary procedures must be performed at the most skilled level. We describe and discuss two cases of iatrogenic complications and the benefits and disadvantages of guidelines. The creation of guidelines should be placed on a rational and scientific basis.