Data of the H218O/H216O ratios of must and wines from the most important German wine areas demonstrate that the statistical scattering of the isotope ratios is large, comparing subsequent years and including tendencies during the harvest period. Before a representative set of vineyards and grapes can be selected, the factors on which the variation depends must be known exactly. The statistical variation which we have measured between the single deliveries of grapes will be preserved during the whole procedure of wine making.