The present invention relates to antibodies that bind CD33. More particularly, the invention relates to anti-CD33 antibodies, fragments and homologues of these antibodies, humanized and resurfaced versions of these antibodies, functional equivalents and improved versions of these antibodies, immunoconjugates and compositions comprising these antibodies, and the uses of same in diagnostic, research and therapeutic applications. The invention also relates to a polynucleotide encoding these antibodies, vectors comprising the polynucleotides, host cells transformed with polynucleotides and methods of producing these antibodies.