I boiled about 1/2 a cup full in a couple of minutes and the cup survived without any seemless adverse affects. You do have to careful though with regards to the stability of the Sigg cup on the stove. Also with the handles being quite small are thus nearer the heat of the stove flame so some care should be used lifting the mug. Overall the mug is useable but not ideal for boiling water. Also the mug seems to creak (sound) when the stove flame was turned down. I'm not to sure whether this was due to the stove or the mug e.g. the dissimilar stainless steel and nickel bronze brazing material used to weld the cup together.