Methods of model-free linkage analysis do not require a detailed specification for the mode of inheritance of the trait locus being linked. Beginning with methods proposed by Penrose in the 1930s, which allowed detection of linkage only, these methods now allow one to use multipoint analysis both to locate trait genes and to estimate variance components that give information on the genetic mechanism underlying the trait. The newer methods can utilize data on multiple types of pairs of relatives other than just sibpairs, and they can detect multiple trait loci. In combination with special sampling schemes, these methods give hope that they may play a crucial role in unraveling the genetic etiology of multifactorial traits, regardless of whether epistatic interactions are present. The results of such analyses can guide the use of more powerful model-based linkage analyses.