This book describes the theory and practice of methods for quantitative trait loci (QTL) detection and analysis, as well as marker assisted selection, in animal genetics and breeding. It is divided into 16 chapters: historical overview; principles of parameter estimation; random and fixed effects (the mixed model); experimental designs to detect QTL (generation of linkage disequilibrium); QTL parameter estimation for crosses between inbred lines; advanced statistical methods for QTL detection and parameter estimation; analysis of QTL as random effects; statistical power to detect QTL and parameter confidence interval; optimization of experimental designs; fine mapping of QTL; complete genome QTL scans (the problem of multiple comparisons); multiple trait QTL analysis; principles of selection index and traditional breeding programmes; marker-assisted selection (theory); marker-assisted selection (results of simulation studies); and marker-assisted introgression. The book is aimed at graduate students and research workers in quantitative genetics and animal breeding. There is an author index and a detailed subject index.