The ED itself is shift work, but how much time you spend in the ED as a PGY-1 varies from program to program. Check out the thread about interviews (it's a sticky) for more ideas on what different programs offer. While you're in the ED, it is round-the-clock shift work. Some places have 8 hr shifts, some 9s, some 10, and some 12s, but all places will have PGY-1s working around the clock.