Inclusion Criteria:

• Males or females, aged 18 years and over
• Patients meeting the diagnostic criteria for SLE (Appendix 2), according to ACR guidelines (including screening for anti-dsDNA (antibody to native DNA in abnormal titer))
• SLEDAI > 6
• Patients treated with maintenance therapy including azathioprine.
• Patients who are willing and able to participate in the study and from whom written informed consent has been obtained

Exclusion Criteria:

• Creatinine clearance of < 20ml/min
• Patients with any clinically significant infection
• Patients with known hypersensitivity to myfortic ® or to drugs with similar chemical structures
• Patients with a history of malignancy of any organ system, treated or untreated, within the past 5 years whether or not there is evidence of local recurrence or metastases, with the exception of localized basal cell carcinoma of the skin
• Patients with SLE active CNS manifestations or a past history of SLE CNS complications (e.g. psychosis, grand mal seizures)
• Patients who have received prior therapy with mycophenolic acids (MPAs) (e.g. MMF)
• Patients who have received an investigational drug within four weeks prior to study entry
• Females of childbearing potential who are planning to become pregnant, who are pregnant and/or lactating, who are unwilling to use effective means of contraception