PURPOSE: To provide a renal failure-improving agent containing (+)catechin as an active ingredient and having an uremic substancelowering action.

CONSTITUTION: (+)-Catechin of the formula is added as an active ingredient. The (+)-catechin can be extracted from a galenical Rheum spp., tea leaves, etc., and has extremely low toxicity and high safety. The (+)-catechin can be prepared as such or together with the conventional carrier into oral agents such as tablets, capsules, granules or grains or into parenteral agents such as injections or suppositories. The administration amount of the (+)-catechin is 100mg-6g several times a day on oral administration or 1-100mg a day on parenteral administration such as intravenous injection, drip intravenous injection, hypodermic injection and intramuscular injection. The agent is a preservative treating agent capable of inhibiting the progress of chronic renal failures and of preventing or retarding the introduction of dialysis.