Internalized homonegativity (IH) is the internalization of negative attitudes and assumptions about homosexual people by homosexual people themselves. To measure IH, Smolenski, Diamond, Ross, and Rosser (2010) and Ross, Rosser, and Smolenski (2010) revised the Reactions to Homosexuality Scale (RHS) to develop the Short Internalized Homonegativity Scale (SIHS) with eight items. Using the European Men Who Have Sex With Men Internet Survey (EMIS) data, with an analytic sample of 130,718 gay and bisexual men in 38 European countries, we confirmed the validity of the SIHS scale in both training and validation data, in strata of Ross, Berg, et al.'s (2013) three "homosexual discrimination" country clusters, of age, and of education level. However, the performance was less adequate in comparison of gay versus bisexually identified individuals. The latent SIHS structure contains only minor variations across these three strata. The seven-item scale performed as well as the eight-item scale. The SIHS is a promising candidate for standard IH measures, which is invariant across cultural, age, and educational strata.