This document provides information on urinary catheterization including the purposes, sizes, types, procedures for insertion and maintenance of catheters. Catheterization is done to relieve urinary retention, obtain urine samples, empty the bladder before or after surgery, and monitor urine output. Catheters come in different sizes depending on use for children, females or males. Procedures are described for inserting foley catheters in males and females which must be done aseptically to prevent infection. Maintaining catheters and the process for removal are also outlined.