|   | 1. | I                      have reviewed this quarterly report on Form 10-Q of Express                      Scripts,                      Inc.; |
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|   | 2. | Based                      on my knowledge, this quarterly report does not contain any                      untrue                      statement of a material fact or omit to state a material fact                      necessary to                      make the statements made, in light of the circumstances under                      which such                      statements were made, not misleading with respect to the period                      covered by                      this quarterly report; |
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|   | 3. | Based                      on my knowledge, the financial statements, and other financial                      information                      included in this quarterly report, fairly present in all material                      respects                      the financial condition, results of operations and cash flows                      of the                      registrant as of, and for, the periods presented in this quarterly                      report; |
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|   | 4. | The                      registrant's other certifying officers and I are responsible                      for                      establishing and maintaining disclosure controls and procedures                      (as                      defined in Exchange Act Rules 13a-15(e) and 15d-15(e), for                      the registrant                      and have: |
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|   | a) | designed                      such disclosure controls and procedures, or caused such disclosure                      controls and procedures to be designed under our supervision,                      to ensure                      that material information relating to the registrant, including                      its                      consolidated subsidiaries, is made known to us by others within                      those                      entities, particularly during the period in which this quarterly                      report is                      being prepared; |
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|   | b) | designed                      such internal control over financial reporting, or caused such                      internal                      control over financial reporting to be designed under our supervision,                      to                      provide reasonable assurance regarding the reliability of financial                      reporting and the preparation of financial statements for external                      purposes in accordance with generally accepted accounting                      principles; |
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|   | c) | evaluated                      the effectiveness of the registrant's disclosure controls and                      procedures                      and presented in this quarterly report our conclusions about                      the                      effectiveness of the disclosure controls and procedures, as                      of the end of                      the period covered by this report based on such evaluation;                      and |
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|   | d) | disclosed                      in this quarterly report any change in the registrant's internal                      control                      over financial reporting that occurred during the registrant's                      most recent                      fiscal quarter (the registrant's fourth fiscal quarter in the                      case of an                      annual report) that has materially affected, or is reasonably                      likely to                      materially affect, the registrant's internal control over financial                      reporting; and |
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|   | 5. | The                      registrant's other certifying officers and I have disclosed,                      based on our                      most recent evaluation of internal control over financial reporting,                      to                      the registrant's auditors and the audit committee of registrant's                      board of                      directors (or persons performing the equivalent                      function): |
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|   | a) | all                      significant deficiencies and material weaknesses in the design                      or                      operation of internal control over financial reporting which                      are                      reasonably likely to adversely affect the registrant's ability                      to record,                      process, summarize and report financial information;                      and |
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|   | b) | any                      fraud, whether or not material, that involves management or                      other                      employees who have a significant role in the registrant's internal                      control                      over financial reporting. |
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