['We have established 17 Y chromosome consomic (Y-consomic) mouse strains in an inbred DH/Sgn strain. In this study, based on investigations in four different genetic backgrounds, we proved that the Y chromosome of the inbred mouse KK/Ta strain is associated with reduced body size.', 'In the DH-Chr Y-+/+ background, Y chromosome substitution significantly decreased the body weight in DH-Chr Y(KK)-+/+ and DH-Chr Y(SJL)-+/+ strains, and the DH-Chr Y(KK)-+/+ strain was the lightest among the 17 Y-consomic strains. In the DH-Chr Y-Dh/+ background (Dh/+ mice have skeletal malformations and are usually lighter than +/+ mice), although Y chromosome substitution did not significantly alter the body weight, the DH-Chr Y(KK)-Dh/+ strain was the lightest among the 17 Y-consomic-Dh/+ strains. In the (B6.Cg-A(y) × DH-Chr Y) F1-+/+ background, Y chromosome substitution significantly decreased the body weight and length in the (B6.Cg-A(y) × DH-Chr Y(KK)) F1 hybrids. In the (B6.Cg-A(y) × DH-Chr Y) F1-A(y)/+ background (Ay causes obesity and promotes linear growth), Y chromosome substitution significantly decreased body weight and length in the (B6.Cg-A(y) × DH-Chr Y(KK)) F1-A(y)/+ hybrids.'] Is y chromosome of the inbred mouse KK/Ta strain associated with reduced body size in Y-consomic strains?