Research and publications on the potato crop have burgeoned since the first edition of this book was published in 1978. However, the warm reception of the first edition suggested that it had a useful part to play in promoting the scientific basis for understanding and improving the yield and quality of the crop. Since the first edition was out of print and a second reprint would not have taken into account the contributions made by research over the intervening years, it became obvious that a complete revision was necessary. There was, in particular, a need to take account of the rapid extension of interest in the crop into climates and farming systems with which it has not been traditionally associa,ted. Those involved with the crop will be sadly aware that a number of contributors to the first edition are no longer with us. Their contribution to our knowledge of the crop will however be a permanent legacy of their achievement. I would like to thank all those who have contributed to the book for their willingness to cooperate in the difficult task of bringing their particular subject up to date. This is even more noteworthy for the pressure of time appears to be almost an order of magnitude higher than it was when the first edition was tackled.