The use of formaldehyde gas is an alternative for the sterilization of thermolabile instruments. A report is given on the effectivity of a sterilization medium the production of which is not dependent on any imports, and on the suitability of sterile packaging materials produced in the GDR for this process. In further studies the formaldehyde residue on catheters and tubing used in urology following sterilization is measured. The question of whether formaldehyde residue on catheters is of toxicological significance is examined.