An IL- 1.beta. binding antibody or IL- 1.beta. binding fragment thereofcomprising the amino acid sequence of SEQ ID NO: 2, and related nucleic acids,vectors, cells, and compositions, as well as method of using same to treat orprevent a disease, and a method of preparing an affinity matured IL- 1.beta.binding polypeptide. IL- 1.beta.binding antibodies or IL- 1.beta. bindingfragments thereof are provided which have desirable affinity and potency.