This text provides a guide to the experimental and analytical methodologies available to study quantitative traits, a review of the genetic control of quantitative traits, and a discussion of how this knowledge can be applied to breeding problems and evolution.1 Introduction. 2 Basic generations - means. 3 Basic generations - variances. 4 Selfing and full-sib mating. 5 Half-sib mating designs. 6 Genes, genetic markers and maps. 7 Gene counting and location. 8 Designer chromosomes. 9 Populations. 10 The consequences of linkage. 11 Epistasis. 12 Genotype by environment interaction. 13 Maternal effects and non-diploids. 14Correlated and threshold characters. 15 Applications. 16 Experimental design