Book excerpt: Sequence data--either lists of nucleotides or of amino acids--are now easily gathered using automated equipment; the real effort is involved in interpreting the data to produce predictions of protein structure or function. With the advent of worldwide computer networks, a plethora of software is now available for sequence analysis. This book describes the techniques for computer analysis of sequence data, with the emphasis on general issues rather than specific algorithms. Unlike many books on these topics, which focus on the "how-to" aspects of software packages, this one places more emphasis on the science behind the packages and on interpretation of the results.