Genstat is the latest version of the statistical package Genstat. This volume, written by the same group who devised the package, is intended to be the primary reference source for all Genstat 5 users. Genstat is a package which has been used particularly by biologists and agricultural workers faced with a range of statistical problems. The aims of its design have been to simplify and rationalize the syntax, to make interactive use more convenient and to extend the statistical, programming and graphical facilities. Statistical facilities include: regression (linear and generalized linear models, non-linear models), analysis of designed experiments (all generally-balanced designs), multivariate analysis (including principal-component, canonical-variate and principal-co-ordinate analyses) and cluster analysis (hierarchical and non-hierarchical classifications) and time series analysis (Box-Jenkins ARIMA models and spectral analysis methods). Other facilities cover data manipulation, calculations, text handling, tabulation and graphics (point and line plots, histograms, contour plots and pie charts). Genstat's command language also has all the attributes of a general-purpose computing language, aiming to allow its facilities to be modified and extended and new forms of analysis to be devised.