An isolated human antibody, or antigen-binding fragment thereof, wherein the antibody or antigen-binding fragment thereof specifically binds to ErbB2 and inhibits ErbB2 phosphorylation in MCF7 cells with a EC50 of less than 50 ng/m1, wherein the antibody or antigen binding fragment thereof comprises heavy chain CDR1, CDR2 and CDR3 amino acid sequences and light chain CDR1, CDR2 and CDR3 amino acid sequences, wherein the three heavy chain CDRs and the three light chain CDRs are selected from the group consisting of: (a) the three CDRs from a heavy chain amino acid sequence of SEQ ID NO: 6, and the three CDRs from a light chain amino acid sequence of SEQ ID NO: 8; (b) the three CDRs from a heavy chain amino acid sequence of SEQ ID NO: 14, and the three CDRs from a light chain amino acid sequence of SEQ ID NO: 16; (c) the three CDRs from a heavy chain amino acid sequence of SEQ ID NO: 18, and the three CDRs from a light chain amino acid sequence of SEQ ID NO: 20; (d) the three CDRs from a heavy chain amino acid sequence of SEQ ID NO: 22, and the three CDRs from a light chain amino acid sequence of SEQ ID NO: 24; (e) the three CDRs from a heavy chain amino acid sequence of SEQ ID NO: 26, and the three CDRs from a light chain amino acid sequence of SEQ ID NO: 28; (f) the three CDRs from a heavy chain amino acid sequence of SEQ ID NO: 30, and the three CDRs from a light chain amino acid sequence of SEQ ID NO: 32; (g) the three CDRs from a heavy chain amino acid sequence of SEQ ID NO: 34, and the three CDRs from a light chain amino acid sequence of SEQ ID NO: 36; or (h) the three CDRs from a heavy chain amino acid sequence of SEQ ID NO: 38, and the three CDRs from a light chain amino acid sequence of SEQ ID NO: 40, wherein the CDRs are as defined by Kabat, and wherein said CDR regions have less than three conservative amino acid substitutions and/or a total of three or fewer non-conservative amino acid substitutions, wherein each amino acid substitution is selected from the group consisting of (i) substitution of a non-germline residue with a germline residue; (ii) substitution to eliminate asparagine-glycine pairs; (iii) substitution to remove an unpaired cysteine; (iv) substitution of a germline residue with a non-germline residue; and (v) conservative substitution. (a) the three CDRs from a heavy chain amino acid sequence of SEQ ID NO: 6, and the three CDRs from a light chain amino acid sequence of SEQ ID NO: 8; (b) the three CDRs from a heavy chain amino acid sequence of SEQ ID NO: 14, and the three CDRs from a light chain amino acid sequence of SEQ ID NO: 16; (c) the three CDRs from a heavy chain amino acid sequence of SEQ ID NO: 18, and the three CDRs from a light chain amino acid sequence of SEQ ID NO: 20; (d) the three CDRs from a heavy chain amino acid sequence of SEQ ID NO: 22, and the three CDRs from a light chain amino acid sequence of SEQ ID NO: 24; (e) the three CDRs from a heavy chain amino acid sequence of SEQ ID NO: 26, and the three CDRs from a light chain amino acid sequence of SEQ ID NO: 28; (f) the three CDRs from a heavy chain amino acid sequence of SEQ ID NO: 30, and the three CDRs from a light chain amino acid sequence of SEQ ID NO: 32; (g) the three CDRs from a heavy chain amino acid sequence of SEQ ID NO: 34, and the three CDRs from a light chain amino acid sequence of SEQ ID NO: 36; or (h) the three CDRs from a heavy chain amino acid sequence of SEQ ID NO: 38, and the three CDRs from a light chain amino acid sequence of SEQ ID NO: 40,