Inclusion Criteria:

• Able to provide informed consent
• Participated in a previous study of sargramostim in Crohn's disease within the past 12 months
• Subjects who participated in protocols excluding concomitant steroid use:
• Must have moderately to severely active Crohn's disease at time of screening (CDAI score >/= 220 points and less than or equal to 475 points)
• Must be receiving less than or equal to 40 mg prednisone (or equivalent) daily at time of screening if treated with corticosteroids between completing their previous sargramostim study and entry into this study and be able to taper to less than or equal to 7.5 mg daily within one treatment cycle
• Subjects who participated in Protocol 307501
• Must have active Crohn's disease (CDAI score > 150 points and less than or equal to 450 points) if completely withdrawn from CS use
• Must be receiving less than or equal to 40 mg prednisone (or equivalent) daily at time of screening, be able to taper to less than or equal to 7.5 mg daily within 2 treatment cycles, and have a CDAI score less than or equal to 450 points if not completely withdrawn from CS use
• Have a negative serum pregnancy test within 2 weeks prior to receiving initial dose of sargramostim in female subjects of child-bearing potential (optional - may be waived by the investigator if the subject has had no interruption in contraception method since participation in the previous study)
• Agree to use of an adequate method of contraception throughout the study period for sexually-active males and females of childbearing potential
• Able to self-inject sargramostim or have a designee who can do so
• Able to comply with protocol requirements
• Have a negative stool exam if subject received a course of antibiotics since participation in the previous study

Exclusion Criteria:

• Pregnant or breastfeeding female
• Need for gastrointestinal (GI) surgery for active GI bleeding, peritonitis, intestinal obstruction, or intra-abdominal or perianal abscess requiring surgical drainage
• Gastrointestinal surgery within the prior 6 months
• Symptoms of bowel obstruction or confirmed evidence of a clinically-significant stricture within the last 6 months that has not been surgically corrected
• Serum creatinine greater than or equal to 2.0 mg/dL
• Alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), or total bilirubin greater or equal to 2X the upper limit of normal; hemoglobin (Hb) < 8.0 gm/dL; platelet count greater than or equal to 800,000/mL; ANC less than or equal to 1,000/µL or > 20,000/µL (the exclusion of subjects with ANC > 20,000/µL applies only to entry into the first treatment cycle)
• Use of licensed/registered anti-tumor necrosis factor (TNF) therapy such as infliximab within 8 weeks prior to first dose of study drug in this trial
• Use of any of the following medications within 4 weeks prior to receiving the first dose of study drug: 6-mercaptopurine, azathioprine, cyclophosphamide, methotrexate, mycophenolate mofetil, tacrolimus, cyclosporine, or thalidomide
• Use of any experimental agent in a clinical trial since participating in a sargramostim trial
• History of allergy to yeast products or sargramostim
• Psychiatric illness or substance abuse that would interfere with ability to comply with protocol requirements or give informed consent
• Clinically important primary disease unrelated to Crohn's disease
• Prior exposure to natalizumab (Tysabri)