In Tsukuba and Tsumagoi (Japan) rates of outcrossing of sweet corn varieties varied by years and locations between 0.1 and 1.2% at a distance of 50 m, and 0.04% at a distance of 400 m (Matsuo et al., 2004). In recent multi-field trials, throughout England, samples of conventional maize stands in a distance of 150 m to GM-maize showed evidence of cross-pollination in 19 out of 44 fields; of these, 12 had >0.1% GM-DNA and 7 had >0.3% GM-DNA (Henry et al., 2003). In several fields the level of gene flow showed a marked increase at distances of 100–150 m from the GM source. This may have been due to the effects of the landscape and the air movement over the crop. Luna et al. (2001) also found in Mexico more cross-pollination at a distance of 200 m from the source than at the shortest distance of 100 m.