Genetic constraints on adaptive evolution can be understood as those genetic aspects that prevent or reduce the potential for natural selection to result in the most direct ascent of the mean phenotype to an optimum. The contributions to this volume emphasize how genetic aspects in the transmission of traits constrain adaptive evolution. Approaches span from quantitative, population, ecological to molecular genetics. Much attention is devoted to genetic correlations, to the maintenance of quantitative genetic variation, and to the intimate relation between genetics, ecology, and evolution. This volume addresses all evolutionary biologists and explains why they should be wary of evolutionary concepts that base arguments purely on phenotypic characteristics.