THE PRESENT INVENTION PROVIDES SALT FORMS OF (R)-3-(4-(7H-PYRROLO [2, 3-D] PYRIMIDIN-4-YL)-1H-PYRAZOL-1-YL)-3-CYCLOPENTYLPROPANENITRILE THAT ARE USEFUL IN THE MODULATION OF JANUS KINASE ACTIVITY AND ARE USEFUL IN THE TREATMENT OF DISEASES RELATED TO ACTIVITY OF JANUS KINASES INCLUDING, FOR EXAMPLE, IMMUNE-RELATED DISEASES, SKIN DISORDERS, MYELOID PROLIFERATIVE DISORDERS, CANCER, AND OTHER DISEASES.