The invention provides for the production of several humanized murine antibodies specific for the Lewis b antigen, which is recognized by the murine antibody 58-1066. The antigen is expressed on cell lines from colon, lung, bladder, breast, renal, pancreatic and ovarian cancers. The expression of the antigen is greatly increased in cancer tissues as compared to its expression in the corresponding normal tissue. The invention also provides for numerous polynucleotide encoding humanized Lewis b antigen specific antibodies, expression vectors for producing humanized Lewis b antigen specific antibodies, and host cells for the recombinant production of the humanized antibodies. The invention also provides methods for detecting cancerous cells (in vitro and in vivo) using humanized Lewis b antigen specific antibodies. Additionally, the invention provides methods of treating cancer using Lewis b antigen specific antibodies.