Antibodies have been obtained against specific fractions of the nuclear lamina from chick red blood cells. Immunofluorescent staining of acrylamide gels from nuclear lamina preparations revealed a spectrum of at least 8-10 proteins cross-reacting immunologically with each other. These proteins are not the result of proteolysis in the course of preparation. the antigens are localized in the nuclear periphery and do not extend into the chromatin. Interspecies cross-reactions enabled us to localize the antigens in the envelope of Xenopus oocyte nuclei. In this case any association with the chromatin is unlikely. During mitosis the antigens are released from the nuclear lamina and and are recovered from the postmicrosomal supernatant. The molecular weights of the nuclear lamina proteins do not change during mitosis.