Like DGTLGRL said: I hate running, I only do it because I'd be 300lbs if I didn't. I used to max out at 2 miles, but I run 10ks about 2-3times a week now as part of my regular training. I did my first half marathon last week.* You basically just work up to it. I mean, I used to just run for 20 minutes, at whatever pace I could muster on the elliptical. I was "running" 6:30 miles on the elliptical - so I knew that was off. So, I decided to 'hate my knees' as maxpower so succinctly put it and switch over to the treadmill. I was in shape enough when I started that I'd run 3 miles no problem, then I started running outside with a couple of coworkers who regularly run marathons and half-marathons - on their 'training runs' of 4-5 miles, then I'd go out with them on 6-7 miles days. I'm not as fast as them, but our last run this season (I only run outside when I can wear shorts/t-shirt) I finished about 48 minutes to the fastest guy at 44 minutes - and I've got 50-60lbs on that guy (I weigh 210lbs). Hell, one of the guys I run with finished a 5k run under 20 minutes pushing both his kids in a double-stroller. I was lucky enough to have coworkers who were encouraging, and the best advice they gave me is that the distance is more important than the time... the lower times will come, but whatever you do - if you set your heart on 5 miles, GO 5 miles. And whatever you do, do NOT walk... it can be the slowest jog in the world, but do not break stride and begin walking. So now - like I said, I'm 210lbs, and my PRs are a 5k @ 20:55, 10k @ 44:55, and my one and only half marathon so far is 1:49:48* *Note: This is all on a treadmill because I'm a 'numbers' guy I need to track my progress and use the treadmill as a relative gauge. Running outside on pavement is NOT equal to a treadmill. Like Nike says: "Just Do it"