The escape of engineered genes - genes inserted using recombinant DNA techniques - from cultivated plants to wild or weedy relatives has raised concern about possible risks to the environment or to health. The media have added considerably to public concern by suggesting that such gene escape is a new and rather unexpected phenomenon. However, transfer of engineered genes between plants is not at all surprising, because it is mediated by exactly the same mechanisms as those responsible for transferring endogenous plant genes: it takes place by sexual crosses, with pollen as the carrier. Such sexual reproduction has been the basis for breeding almost all crops.