The Habanero chile is the most intensely spicy chile pepper of the Capsicum genus. Most habaneros rate 200,000–300,000 Scoville heat units (SHU), and the Red Savinas variety, at 580,000 SHU, holds the record for being the "World's Hottest Spice".

Scoville's original method for testing hotness was called the Scoville Organoleptic Test, which he developed in 1912. As originally devised, a solution of the pepper extract is diluted in sugar water until the "heat" is no longer detectable to a panel of (usually five) tasters; the degree of dilution gives its measure on the Scoville scale. Thus a bell pepper, containing no capsaicin at all, has a Scoville rating of zero, meaning no heat detectable even undiluted. Conversely, the hottest chiles, such as habaneros, have a rating of 300,000 or more, indicating that their extract has to be diluted 300,000-fold before the capsaicin present is undetectable. The greatest weakness of the Scoville Organoleptic Test is its imprecision, because it relies on human subjectivity.