Idiopathic CD4+T lymphocytopenia (ICL) is a rare immune deficiency with heterogeneous clinical manifestations. This syndrome first described in 1992 and defined as absolute CD4+T-lymphocyte count<300/mm3 or less than 20% of total lymphocytes that confirmed at least twice during a period of 1 to 3 months in the absence of HIV-1 infection disease or any other cause of immunodeficiency. Patients with ICL often presents with opportunistic infections, malignancies, or autoimmune disorders and the major risk ICL is unexpected infections, including cryptococus, atypical mycobacterial and pneumocystis pneumonia (PCP). In some patients also additional immunologic defects including CD8+lymphocytopenia and low immunoglobulin levels was occur. This disease was seen in both children and adults and two genders. At present the etiology of disease is unknown and also it does not appear to be caused by a transmissible agent, such as a virus, but it is widely believed that there is more than one cause. Although in general, prognosis of disease is depends on absolute number of CD4, but in contrast to the CD4+cell depletion caused by HIV, patients with idiopathic CD4 lymphocytopenia have a good prognosis. The decline in CD4+T-cells in patients with ICL is generally slower than that seen in HIV-infected patients and in some cases this condition may also resolve on its own. We present 3 cases of ICL with different prognosis.