To improve the accuracy of early diagnosis of retinoblastoma, the authors have examined a number of cellular and humoral immunity parameters in 188 children with retinoblastomas, in 57 ones with nontumorous conditions of the eyes, and in healthy controls. Stages III-IV retinoblastoma was found associated with reduced blood levels of IgG and IgA and a still more marked reduction of both in the lacrimal fluid (4-fold), with reduced blood T lymphocyte count (by 1.5 times), decreased lymphocyte blastogenesis response to phytohemagglutinin (by 8-9 times), reduced leukocyte migration activity (MI = 79 +/- 10%), reduced serum thymic activity (by 2.5 times). The early (I-II) stage of the disease involves a lowering of only lacrimal fluid IgA (2-fold) and of the leukocyte migration index (MI) (89 +/- 2%). This index was found to be an important specific indicator for the early preoperative diagnosis of retinoblastoma. Leukocyte migration inhibition (MI less than 95%) by retinoblastoma antigens was observed only if this tumor was present. In cases with the nontumorous conditions and in health retinoblastoma antigens as a rule stimulated the leukocyte migration (MI over 95%).