Antibodies that bind CSF1R are provided. Antibody heavy chains and light chains that are capable of forming antibodies that bind CSF1R are also provided. Polynucleotides encoding antibodies to CSF1R are provided. Polynucleotides encoding antibody heavy chains and lights chains are also provided. Methods of treatment using antibodies to CSF1R are provided. Such methods include, but are not limited to, methods of treating rheumatoid arthritis, bone loss, and multiple sclerosis.