The hypothesis that gene flow northwards by long distance wind dispersal of pollen is a contributing factor in Scots pine (Pinus sylvestrisL.) seed crops in northern Scandinavia (Umeå) was examined. Pollen was observed in the air before local pollen shedding began. This pollen has been shown to germinate and is likely to be viable. This early pollen was probably not of local origin. Wind patterns and the geographic pattern of pollen shedding were such that it is likely that the origin of the early pollen was hundreds of km to the south. Since many of the female strobili are receptive to pollination before local pollen shedding occurred, early non-local pollen has an advantage over later local pollen. Thus, the gene flow caused by pollen migration is likely to be large enough to be of evolutionary significance.