Member states will impose strict technical management measures to keep the adventitious presence of GM material in non-GM produce below the labeling thresholds. As maize is a cross-pollinated crop relying on wind for dispersal of its pollen, on-farm measures may rely on spatial isolation. The task may be difficult, since various biological, physical, experimental, and analytical parameters with varying levels of importance have been identified to play a role in the study of cross-fertilization in maize. The number of variables and their variability may hamper the comparison between research results and make it difficult to define the appropriate length of isolation distances and/or pollen barriers. How some of the parameters can hamper the comparison between research results is addressed below.