In the last decade nucleo-cytoplasmic transport has developed into one of the most active areas of research in cell biology and its significance for cell biology as a whole has been recognized. It has led to elucidation of the mechanisms of major cellular functions such as protein synthesis and cellular differentiation. It is also helping to bring about a synthesis of ultrastructural, biochemical, molecular biological and biophysical approaches to the study of cellular organization and function. These theoretical advances have been made possible chiefly by advances in technology - improved methods of gene manipulation and sequencing, of monoclonal antibody production and the use of protein chemistry, of microscopy and of cell manipulation, including microinjection methods. Developments in molecular biology, such as the search for sequence - specific DNA binding proteins and the identification of their binding domains, have also furthered advances in cell biology and these areas have become increasingly integrated with some well-established areas of biochemistry. This book aims to be an introduction, for senior undergraduates and postgraduate biologists, to the field of nucleo-cytoplasmic transport and its relevance to cell biology and seeks to use recent advances in the field to illustrate the process by which modern scientific progress occurs - the importance of developing techniques for formulating problems as well as answering them and the integration of different approaches leading to the evolution of novel concepts. The author assumes a basic general knowledge of molecular and cell biology and of biochemistry, but provides all the necessary background for discussion of recent advances and in the final chapters discusses the actual and potential contributions of the field of nucleo-cytoplasmic transport to cell biology.