Lifelong immunoglobulin replacement is the standard, expensive therapy for severe primary antibody deficiencies. This treatment can be administrated either by intravenous immunoglobulin (IVIG) or subcutaneous infusions (SCIG) and delivered at home or in an out-patient setting. This study aims to determine whether SCIG is cost-effective compared with IVIG from a French social insurance perspective. Because both methods of administration provide similar efficacies, a cost-minimization analysis was performed. First, costs were calculated through a simulation testing different hypothesis on costs drivers. Secondly, costs were estimated on the basis of field data collected by a questionnaire completed by a population of patients suffering from agammaglobulinaemia and hyper-immunoglobulin (Ig)M syndrome. Patients' satisfaction was also documented. Results of the simulation showed that direct medical costs ranged from 19 484 euro for home-based IVIG to 25 583 euro for hospital-based IVIG, with home-based SCIG in between at 24 952 euro per year. Estimations made from field data were found to be different, with significantly higher costs for IVIG. This result was explained mainly by a higher immunoglobulin mean dose prescribed for IVIG. While the theoretical model showed very little difference between SCIG and hospital-based IVIG costs, SCIG appears to be 25% less expensive with field data because of lower doses used in SCIG patients. The reality of the dose difference between both routes of administration needs to be confirmed by further and more specific studies.