Adults and children with primary antibody deficiencies are prone to bacterial infections affecting the respiratory tract and gastrointestinal canal. To prevent or alleviate infections, replacement therapy with IgG is needed, usually on a lifelong basis. The IgG can be administered intramuscularly, intravenously, or subcutaneously. Subcutaneous IgG (SCIG) therapy, using small portable pumps for once-per-week self infusions, has shown many advantages compared with the two other routes of administration. This review highlights findings from international studies and demonstrates that: (i) SCIG therapy is safe, with very few adverse effects; (ii) the therapy can be used for patients with previous adverse effects to intravenous administration of IgG; (iii) the therapy leads to high serum IgG levels and good protection against infections; (iv) the therapy facilitates home therapy, as the infusion technique is easy for children, adults and elderly people to learn and there is no need for venous access; (v) SCIG home therapy leads to significantly improved life situations for the patients; (vi) the SCIG home therapy regimen in particular reduces the costs of treatment.