Michael Phelps has entered four events at next week’s U.S. national championships.

Less than four months after coming out of retirement, Phelps will compete in the 100-meter freestyle, 100 butterfly, 100 freestyle and 200 individual medley at the meet in Irvine, California.

The national championships, along with the Pan Pacific Championships in Australia a couple of weeks later, will determine the American team for next year’s world championships.

The 29-year-old Phelps is the most decorated Olympic athlete with 18 gold medals and 22 medals overall. He retired after the London Games, having accomplished all his goals and saying he had no desire to swim into his 30s.

But he began plotting a comeback less than a year later. Since returning, he has competed in four meets.