The present invention provides stabilized immunoglobulin molecules that have increased storage stability and/or in vivo half-lives due to the mutation of one or more amino acids that would otherwise render the immunoglobulin molecules susceptible to degradation. In a preferred embodiment, the stabilized immunoglobulins of the invention have mutations at the heavy chain constant domain hinge region. Such stabilized immunoglobulin molecules, i.e., immunoglobulin molecules with increased storage stability have one or more of the following advantages they are more readily transported and/storable for longer periods and/or less stringent conditions than non-stabilized counterparts; that smaller amounts and or less frequent dosing is required in the therapeutic, prophylactic or diagnostic use of such stabilized molecules.