Antibodies having dual specificity for two different but structurally related antigens are provided. The antibodies can be, for example, entirely human antibodies, recombinant antibodies, or monoclonal antibodies. Preferred antibodies have dual specificity for IL-1.alpha. and IL-1.beta. and neutralize IL-1.alpha. and IL-1.beta. activity in vitro and in vivo. An antibody of the invention can be a full-length antibody or an antigen-binding portion thereof. Methods of making and methods of using the antibodies of the invention are also provided. The antibodies, or antibody portions, of the invention are useful for detecting two different but structurally related antigens (e.g., IL-1.alpha. and IL-1.beta. ) and for inhibiting the activity of the antigens, e.g., in a human subject suffering from a disorder in which IL-1.alpha. and/or IL-1.beta. activity is detrimental.