Since I edited Combinatorial Peptide and Nonpeptide Libraries - the first comprehen-
sive book on the subject - in 1996, progress in the field of combinatorial chemistry has
been truly dramatic. However, before I began to write this preface, I looked back and
found the early work by no means outdated - as evidenced by the number of complimen-
tary letters received from satisfied readers. A number of excellent books on combinatori-
a1 chemistry have appeared since then, covering different aspects of the subject. How-
ever, despite this earlier ‘boom’, I was encouraged to edit a second volume, and recog-
nized that soon there will be very little overlap of Cornhinutorial Chemistry with the con-
tents of other such books.