This paper describes information-handling aspects of the TYCHO I analysis system (Clin, Chem. 27: 1807--1820, 1981), which analyzes two-dimensional electrophoresis gels, matches the individual protein spots with those in a reference pattern, and stores various information--including spot measurements, identifications, treatment profiles, set memberships, and comments--in a computerized database. This and additional information such as amino acid composition and cellular localization is then accessible from an interactive program that includes a pictorial user interface and presents much of the data in graphical form. Use of the TYCHO I system is illustrated by examples drawn from analyses of gel patterns from human leukocytes.