We have presented two cases strongly suporting a Y chromosome short-arm location for the H-Y antigen gene. The first case was HY antigen-positive with an isochromosome for the short arm of the Y with no long arm of the Y being present. The other case was H-Y antigen-negative in fibroblasts from an individual with a 46,X,i(Yq) karyotype with no short arm of the Y present. The two cases presented also confirmed previous reports that the testicular forming gene is also located on the short arm of chromosome Y.