Extremely hot! This sauce is no joke. My dad tried a spoonful of it while he was working up in Alaska. Big mistake. He couldn't breathe. It nearly sent him to the hospital. I was smart enough to put some on a spoon and then dip the tip of my tongue into it, not try and eat a whole spoonful. This sauce is extremely thick and concentrated. It barely runs out of the bottle without some shaking for encouragement. It has a very bitter pepper extract flavor up-front, with a touch of smoky habanero. If you can get over the nasty bitterness, you might even be encouraged to try some more. Don't. Then, the burn hits. After tasting just a little of this, you will need milk. Like, five glasses of milk. And it's oily and the milk just spreads it around your mouth and makes the burn worse, at first. If you like spicing up your food, this is very economical; a teaspoon will make any dish almost inedibly hot for most people. One bottle will last a very, very long time. Don't be dismayed by the gross flavor; when diluted in a bowl of chili con carne, the bitterness vanishes.