Scrape off excess ketchup with a dull butter knife. This will allow you to remove both wet and dry ketchup without spreading it on other areas of your clothing.
Run cold water from the back of the stain. This will force some of the ketchup out of the clothing.
Rub a liquid laundry detergent onto the stain with a cotton ball. This will pre-treat the stain. Let the detergent rest on the stain for five minutes.
Wash the laundry with hot water in your washing machine. Add your regular detergent and 1/2 cup of borax to the washing machine.
Hang the laundry to dry. If you place the clothing in the dryer, it will cause the stain to set in permanently if you did not completely remove it. Repeat pre-treating and washing the clothing until the stain disappears.