A follow-on Safety Study in Subjects With Crohn's Disease Who Have Previously Been Withdrawn From the Double-blind Study CDP870-031 [NCT00152490] or CDP870-032 [NCT00152425] Due to an Exacerbation of Crohn's Disease

Inclusion Criteria:

• Participation in either of the CDP870-031 [NCT00152490] or CDP870-032 [NCT00152425]clinical studies in which the subject completed the Week 2 assessment in CDP870-031 [NCT00152490] or the Week 6 randomization in CDP870-032 [NCT00152425] but whoseCrohn's Disease was significantly worse as determined by the investigator and whoseClinical Disease Activity Index (CDAI) score at entry to this study is either (subjects may have received active or placebo treatment):

1. At least 70 points higher then Baseline (Week 0 CDP870-031 [NCT00152490]; Week 6CDP870 032 [NCT00152425] responders) OR

2. Higher than Baseline (Week 0 CDP870-031 [NCT00152490]; Week 6 CDP870-032 [NCT00152425] responders) with an absolute score of at least 350 points

• Subjects must be able to understand the information provided to them and give writteninformed consent

Exclusion Criteria:

• Any exclusion criterion that would have prevented the subject's participation in thequalifying pivotal study (CDP870-031 [NCT00152490] or CDP870-032 [NCT00152425]),although the upper limit of 450 in the CDAI score is not applicable. In addition thecriterion that excludes previous participation in a clinical trial of CertolizumabPegol does not apply