The increase of total IgE was observed in patients with toxocariasis. Its level can highly exceed the normal level. There is a definite correlation between the level of eosinophilia, the severity of the allergy symptoms and the content of total IgE. The increase of immunoglobulins (IgG and sometimes IgM) is observed in clinically significant toxocarosis (the visceral form). The polyclonal stimulation of B-cell population, manifested by an increase of immunoglobulins of all 3 classes was noted in severe cases of infection and in active immunogenesis. Our study concerns the parameters of humoral immunity in patients with toxocariasis. The study included 52 patients of different age and sex with toxocariasis. The content of IgE (UBI Magiwel company – USA) and IgG, IgA, IgM (company “Vector-BEST (Russia) was determined by ELISA, the content of CD19 lymphocytes – using Flow Cytomertrie (Partec PAS I). All patients received the antiparasitic treatment with albendazole and immune corrective therapy with BioR or Polyoxidonium. The parameters values were expressed in MЃ}ES. The content of CD19 at admission (see table) was significantly higher in patients than in healthy persons (p<0.001), the content of CD19 was significantly decreased after the treatment (p<0.01), but remained at a high level and after the treatment (p<0.001) . The content of IgG, IgA, IgM at admission was significantly higher in patients than in healthy persons (p<0,001), the content of IgG, IgA, IgM after the treatment was significantly decreased (from p<0,05 to p <0,01 according to the index), but remained at a high level after the treatment (from p<0,01 to p <0,001, according to the index). The content of IgE at admission in hospital was significantly higher in patients than in healthy persons (p<0,001), the content of IgE was significantly decreased (p <0,01), but remained at a high level after the treatment (p<0,001). The increase of CD19 and polyclonal stimulation of B-cell population (the increase in all 3 classes of immunoglobulins) were marked in patients with toxocariasis. After the antiparasitic treatment and immune correcting therapy the analyzed indicators decreased significantly, however at hospital discharge they continued to be at significantly higher than in healthy persons. The research results indicate a pronounced lesion of B immunity system in patients with toxocariasis and an insufficient rate of antiparasitic and immune correcting therapy in achieving the cure.