Rudy Giuliani tells ABC News the story of the day he had to leave the campaign trail for the hospital:

Giuliani: It was a terrible headache, I mean all day — it got worse all day. It got really bad at night, when I was speaking to a crowd and did a press conference with Sen Bond. Got on the plane. I imagine what happened is the pressure of the takeoff made the headache worse than I’ve ever had.
Stephanopoulos: Did you black out?
Giuliani: No. My staff was very concerned so we turned around. I actually made that decision. Were only 6 or 7 minutes out. It actually made no sense to get on the plane. I probably thought of it. Once I got on and the pressure got worse I said let’s turn back. They decided, you better really check him out. And they did really check me out.
Stephanopoulos: So what did they check for? What were they worried about?
Giuliani: They checked everything. I mean you’d have to ask my doctor everything they checked for. I mean he put out a statement that I’m in very good health, that every test came back normal. What I’ll do now is – there’s also, I’m a cancer survivor. So there’s always the issue of cancer, so I’m going to have him put out a statement and then you know make everyone really comfortable that I’m okay. But they tell me I’m in very good health.