Genstat 5 Release 3 is the latest version of a popular statistical system that provides statistical summaries, analysis, data-handling, and graphics capabilities. Genstat--used worldwide on personal computers, workstations, and mainframe computers--has become the system of choice among many statisticians, researchers, and students across the many disciplines that use and apply statistics. This system guide has been rewritten for Release 3 and features new, example-rich chapters on basic statistics and on REML. It also clearly and practically details Release 3's many new capabilities, including the analysis of ordered categorical data, generalized additive models, combination of information in multi-stratum experimental designs, extensions to the REML (residual maximum-likelihood) algorithm, estimation of parameters of statistical distributions, further probability functions, simplified data input, and many new extensions for high resolution graphics, calculations, and manipulation. Both novices and seasoned users of Genstat will welcome this well-written, practical guide to Release 3.