If you are usually at a 36 I would go with a large, but if you are usually a 34 I would go with a Medium. That waist size is tough, because that is where the size splits. I am a 34 and can definitely say that it is on the high end of the medium option.

Go with the large, you can always grow into them. :)

I have to agree with 20r. Even if you don't plan on growing into them, it sucks to be too restricted.