Abstract:The concept of a strong difference family formally introduced in Buratti [J Combin Designs 7 (1999), 406-425] with the aim of getting group divisible designs with an automorphism group acting regularly on the points, is here extended for getting, more generally, sharplyvertex-transitive -decompositions of a complete multipartite graph for several kinds of graphs . We show, for instance, that if has e edges, then it is often possible to get a sharply-vertextransitive -decomposition of K m×e for any integer m whose prime factors are not smaller than the chromatic number of . This is proved to be true whenever admits an α-labeling and, also, when is an odd cycle or the Petersen graph or the prism T 5 or the wheel W 6 . We also show that sometimes strong difference families lead to regular -decompositions of a complete graph. We construct, for instance, a regular cube-decomposition of K 16m for any integer m whose prime factors are all congruent to 1 modulo 6.