What's the longest you've gone without sleep?

I once had to work the phone for 36 hours taking media calls from around the world. As we finished deadlines in one time zone, we would come up anew in a the next time zone. It started a little after 5 pm on a long weekend so no one else to back me up. I had already put in an 8 hour workday, so approaching 50 hours. I was taking little short cat naps between calls towards the end when things began to slow down, but not real sleep.