Catheterization is a routine medical procedure that facilitates direct drainage of the urinary bladder. It is used for both the diagnostic and therapeutic purposes. Many types of catheters are available for urethral catheterization, and the choice of a specific type of catheter depends on the reason for catheterization. The catheter for one-time catheterization is usually a straight catheter made from polyvynyl chloride or sometimes latex. For long-term catheterization catheters need a retention mechanism. Foley type catheters (balloon served as retention mechanism) are most often used for long-term urethral catheterization. If long-term catheterization is anticipated, it is advisable to use a Foley catheter made of the most biocompatible material. Catheters made of silicone or coated with hydrogel are, in general, better tolerated over the long-term than those made of materials like latex and polyurethane. In addition, one should choose the smallest urethral catheter that will accomplish the purpose of catheterization. The duration of catheterization must be as short as possible. Difficult catheterization is mostly seen in male patients. The most frequents causes are urethral stricture, prostatic enlargement and bladder neck contracture. Difficulty in catheterization of the female urethra is uncommon and usually results from extreme obesity and inability to locate the urethral meatus. The most frequent complication associated with catheterization is catheter-associated urinary tract infection resulting in significant morbidity and mortality. It is the most common nosocomial infection, comprising >40 % of all institutionally aquired infections. Other possible complications are paraphimosis, creation of false passage, urethral stricture, urethral perforation and bleeding. Catheterization is a routine procedure in the majority of patients but because of potential complications, performance must be standardized.