Previous observations suggested that pituitary dwarfism of German Shepherd dogs is due to simple, autosomal recessive inheritance, but own data were insufficient to test the hypothesis. The total material now includes six dwarfs from five litters. Omitting the proband litter, a total of 21 dogs from four litters, each with one dwarf, were relevant for testing goodness of fit. The observed segregation ratio was in agreement with that expected and thus supported the genetic hypothesis. According to this hypothesis it was possible to point at various heterozygous carriers among ancestors of the dwarfs within a pedigree comprising 13 generations.