The aldehyde residues of thermolabile urological instruments, after the formaldehyde sterilization or sterilization in aseptic preparation from a 2% glutaraldehyde solution will be examined and compared. The results are discussed together with experimental toxicologic work from the literature. It is concluded that after sterilization in the 2% glutaraldehyde solution, the glutaraldehyde residues on the experimental materials are safe.