|   | 1. | I have      reviewed this quarterly report on Form 10-Q of Pharmacyclics,      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 officer 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)) and internal      control over financial reporting (as defined in Exchange Act Rules      13a-15(f) and 15d-15(f)) 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 is made known to us by others      within the registrant, particularly during the period in which this 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 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 report any change in the registrant’s internal control over financial      reporting that occurred during the registrant’s most recent fiscal quarter      that has materially affected, or is reasonably likely to materially      affect, the registrant’s internal control over financial      reporting; |
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|   | 5. | The      registrant's other certifying officer 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  functions): |
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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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| Date:  | February 12,      2010 |                                                                                      | /s/  ROBERT      W. DUGGAN |
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|   |                   |                                                                                      |                                 |
|   |                   | Robert W.      Duggan                                                                     |
|   |                   | Chairman of      the Board and Chief Executive Officer (Principal      Executive Officer) |