Diet Mountain Dew (also known in Denmark and Finland as "Free Mountain Dew", in the U.K. as "Sugar Free Mountain Dew" and in New Zealand as "Mountain Dew No Sugar") is a Mountain Dew variant with only 10 calories, compared to the 290 calories in the original.
Diet Mountain Dew is only a modified version of the original formula, but has the same citrus taste and yellow-green coloring.
Diet Mountain Dew was originally branded as "Sugar-Free Mountain Dew" when it was first released, until 1986, when it received the name it currently has.
In 2006 Diet Mountain Dew was reformulated with a new "Tuned Up Taste", using a blend of sucralose, aspartame, and acesulfame potassium as sweeteners. The previous formulation was sweetened exclusively with aspartame.