Winegrape samples were collected from 2001 to 2003 in vineyards located in the Pacific Northwest. Riesling and Chardonnay had lower concentrations of biotin (often < 1 mu g/L) than did red cultivars. The concentration of pantothenic acid (mean 513 +/- 181 mg/L) was lowest in Riesling but highest in Chardonnay. Most samples contained low amounts of yeast assimilable nitrogen (YAN), ranging from 25 to 336 mg/L (mean 124 +/- 62 mg/L). While most grape samples had adequate amounts of pantothenic acid for fermentation, many were deficient in biotin or YAN. (We recommend that you consult the full text of this article.)