The present invention is directed to a method of selecting a clone that binds to human platelet glycoprotein Ib alpha using a human variable heavy chain and variable light chain immunoglobulin library. The invention is further directed to isolated nucleic acid molecules encoding a variable heavy chain or variable light chain region of an antibody, wherein the antibody binds to human platelet glycoprotein Ib alpha and inhibits aggregation of platelets. Expression vectors and host cells comprising the nucleic acid molecules are also provided, as well as methods for producing the variable heavy chain or the variable light chain region. An isolated variable heavy chain or variable light chain region of an antibody, wherein the antibody binds to human platelet glycoprotein Ib alpha and inhibits aggregation of platelets, is also provided. An antibody comprising the variable heavy chain or variable light chain regions is provided, as is a composition comprising the antibody and a carrier. The subject invention further provides a method of inhibiting aggregation of platelets, as well as a method of binding human platelet glycoprotein Ib alpha. A method of selecting a variable heavy chain or variable light chain region of an antibody is also provided.