I think you mean a sweat test. Don't worry, for your son it will be nice and easy! I was 14 when I had mine done so I am not sure if its a little bit different for a baby, but I will tell you what they did to me. First they put 2 stickers with wires on my arm (sorry I was only 14 and it was years ago so I don't remember anything technical so this will be a dumbed down version <img src="i/expressions/face-icon-small-blush.gif" border="0">) This was painless of course, just felt like a sticker on my arm. They then wrapped my arm up which again was painless. They then told me to sit real still (this may be the "hard" part for a little kid or infant) I can't remember how long I sat there, but basically they just want your arm to sweat (hence sweat test) After you have let your arm sweat enough they unwrap your arm and remove the stickers and it is done! Thats the perspective from a kids point of view which the only thing that was important to me at the time was no needles and no pain! I think the difficult part is that it MUST be done correctly because it can easily be done wrong. The say you should get it at a CF center to ensure the most accurate results. Also, if it is positive you can then get a blood test to find the mutation, this will also confirm the sweat test. I hope someone can explain it better than me, but I just wanted to let you know your son will not be put through anything horrible or painful.Emily