We present 3 patients with chronic renal failure who had postoperative paralysis due to the administration muscle relaxants. One of them received gallamine, a non-depolarizing blocking agent that is mainly excreted by the kidney (70--90%). Two of them received pancuronium bromide, also a non-depolarizing blocking agent which is partially excreted by the kidneys (37--44%). All of them received succinylcholine. Succinylcholine is hydrolyzed by the serum cholinesterase into succinylmonocholine and choline. These active metabolites are excreted by the kidney. These patients serve as examples of the importance of considering the route of excretion of drugs and their metabolites in clinical situations involving the renal failure patient. The pharmacology of drugs administered relative to surgical procedures is reviewed.