Retinoblastoma antigen(RbAg) and retinal tissue antigen(RAg) were made from allogeneic retinoblastoma tissues and normal retinal tissue using the 3M KCl method. We have examined leukocyte migration inhibition test (LMIT) and enzyme-linked immunosorhent assay (ELISA) to RbAg and RAg in normal controls and the patients with retinoblastoma,including two spontaneously regressed cases. In LMIT, six out of the 11 patients tested against RhAg showed positive reactivity, in which 4 cases reacted only with RbAg, but not with RAg. All nine control subjects had negative reactivity to the two antigens. In ELISA, 40% of the retinoblastoma patients and 5.56％ in normal controls showed positive reaction against RbAg. It was suggested that not only retinal antigens but also retinoblastoma specific antigens present in human retinoblastoma cells. The results also suggested that patients with retinoblastoma and those with spontaneous regression of Rb had both cell-mediated immunologic reactivity and humoral immune response toward retinoblastoma antigen in vitro. These immune responses to RbAg may be responsible for spontaneous regression of retinoblastoma. Retinoblastoma antigen (RbAg) and retinal tissue antigen (RAg) were made from allogeneic retinoblastoma tissues and normal retinal tissue using the 3M KCl method. We have examined leukocyte migration inhibition test (LMIT) and enzyme- linked immunosorhent assay (ELISA) RAg in normal controls and the patients with retinoblastoma, including two spontaneously regressed cases. Both LMIT, six out of the 11 patients tested against RhAg showed positive reactivity, in which 4 cases reacted only with RbAg, but not with RAg. All nine control subjects In was 40% of the retinoblastoma patients and 5.56% in normal controls showed positive reaction against RbAg. It was suggested that not only retinal antigens but also retinoblastoma specific antigens present in human retinoblastoma cells. The results also suggested that patients with retinoblastoma and those with spontaneous regression of Rb had both cell-mediated immunologic reactivity and hum oral immune response toward retinoblastoma antigen in vitro. These immune responses to RbAg may be responsible for spontaneous regression of retinoblastoma.