X-linked agammaglobulinemia (X-LA) was the first described and remains the most common inherited antibody deficiency. Although initially reported by Bruton in early fifties, full clinical picture and detailed pathogenesis were established recently. X-LA was the first immunodeficiency to be mapped to a specific locus in the human genome based on linkage analysis. Molecular basis for this disease is more than 400 mutation in one of Tec kinases--Bruton's tyrosine kinase (Btk) which affects B cell maturation through impaired B cell receptor signaling. Although the precise mechanism is still to be elucidated, data obtained from transgenic animals suggested that Btk controls B cell maturation at least in two different levels--in bone marrow and in spleen. Clinical features comprise encapsulated bacteremia and pyremia in boys with very low B lymphocyte count and low immunoglobulin concentrations. Lymphocytes from patients with X-LA are unable to synthesize immunoglobulin in response to T cell-independent antigens. Standard treatment is an immunoglobulin substitution. Gene therapy seemingly may be an ideal treatment for this disease. In this paper authors reviewed current literature describing recent updates in pathogenesis, diagnosis and treatment of X-linked agammaglobulemia.