Will the pure-bred wine please stand up.

[Thomas]

And furthermore, just because a wine is labeled by grape variety doesn't mean it is not blended. The BATF allows a label to carry the name of a grape as long as the wine includes no less than 75 percent of that grape, which leaves 25 percent for anything else the winemaker chooses to blend in.

Good winemaking often requires careful, studied blending, both for consistency in style and to make up for less-than-average vintage years. Before the California wine industry made grape variety names the benchmark for successful marketing, as Innkeeper says, you would have been hard-pressed to find a wine that was identified by the grape varieties in the bottle, except for Germany and Alsace, plus California.