Toxocariasis is one of the causes of eosinophilia in peripheral blood and provokes eosinophilic infiltration in internal organs. In Israel, the number of cases of toxocariasis is very low, 3 cases annually, according to the records at the Ministry of Health. Many cases of eosinophilia might be misdiagnosed as hypereosinophilia syndrome (HES), if serological testing for Toxocara is not conducted, leading to inappropriate treatment. The test is for specific serum IgG antibody of Toxocara canis antigen measured by enzyme-linked immunosorbent assay (ELISA). The authors present a 4 year old girl with hypereosinophilia of 40,000 cell/microl, without involvement of target organs. The authors found that toxocara was the cause of hypereosinophilia. After appropriate treatment the number of eosinophils decreases, presenting a measurement of the parasite activity.