The main concepts of several multivariate statistical methods used for analyzing and classifying stored-grain infestation data observed during a decade's ecological studies is presented briefly in non-mathematical language with simple diagrams to encourage their use by stored-product entomologists. The mathematical assumptions and limitations of cluster analysis, multiple regression analysis, principal component analysis, factor analysis, canonical correlation analysis and discriminant analysis are given. Original examples of application and interpretation of principal component analyses to insect- and mite-infested wheat and rapeseed bulks on western Canadian farms are given, as this method was found to be the most useful hypothesis-formulating tool.