Nearly one in five US youths will run away from home before age 18. Almost 30 percent of these youths will do so three or more times, increasing their risk of violence, crime, drugs, prostitution, sexually transmitted diseases, and other problems. Employing new methodology to yield estimates not available elsewhere, this paper follows a nationally representative sample of 12-year-olds to their 18th birthdays to discover how many youths run away from home, the number of times they run away, and the age they first run away. We found that female and black youths run away most often.