Linkage disequilibrium involving three loci

A formula for the estimation of “three-locus interaction delta” given by Nijenhuis & D'Amaro (1985) is considered and found to be unsatisfactory. An alternative symmetrical formula is given. Other features of the analysis of Nijenhuis & D'Amaro are criticized and it is emphasized that a more suitable method of analysis of interactions of different orders is given by the use of the empirical logistic method (Green et al. 1983).