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Just blot. If you rub the stain, you could lock it into the clothing. Do this if your cat has just urinated on the clothes. You'll have a better chance of removing the smell on the first wash if you can do it while the stain is fresh. Take the affected garment to the sink. Run a stream of cool water over the stain for a few minutes. Blot the stained area dry. Fill a sink with warm water. Add a scoop of oxygen bleach. Place the clothing in the sink. If the clothing is colored, allow it to sit for at least one hour. If it's white, soak it for up to four hours.  This product may be sold as Oxiclean, Vanish, or simply oxygen bleach. Avoid using chlorine bleach. When it combines with the ammonia in urine, it can create harmful gases.
Sop up excess liquid with a cloth or paper towels. Rinse the spot. Pre-treat the stain with oxygen bleach.