Inclusion Criteria:

• men and women with diagnosis of SLE
• 18 years and above
• negative pregnancy test for female subjects of child-bearing age and must accept not to attempt to get pregnant during the period of the study
• Subject with active disease as defined by SLAM of at least 8
• SLICC/ACR damage index of less or equal to 15
• Subject must be on stable does of NSAIDs, prednisone, or antimalarial (chloroquine sulfate or hydroxychloroquine) at least 4 weeks preceding the study
• subjects can be under other medications as long as condition or treatment will not interfere with the experimental medications and assessments
• must understand either French or English and can give written informed consent

Exclusion Criteria:

• previous history of hypersensitivity or intolerance to methotrexate or folic acid
• total SLAM of less than 8 or total SLICC/ACR score of more than 15.
• history of medical non-compliance or inability to comply with instructions
• subject who have received intra-articular or intramuscular corticosteroids in the four weeks prior to study entry.
• clinically significant acute or chronic liver disease with the exception of autoimmune liver disease
• alcohol use in excess of 2 ounces of 100 proof liquor or its equivalent/week
• insulin requiring diabetes mellitus with morbid obesity
• renal impairment such that the serum creatinine is more than or equal to 175 umol/I (SI units) or 2.0 mg/dl
• interstitial lung disease as defined by an abnormal chest x-ray or decrease diffusion capacity (DLCO < 70% of predicted) without evidence of pulmonary hypertension.
• WBC count ,3,000/ cubic mm. and/or platelet count ,80,000/ cubic mm.
• prior use of methotrexate to treat SLE
• use of sulfa drugs that may potentiate the folate antagonistic effects of MTX
• non-steroidal anti-inflammatory drugs will be allowed throughout the trial unless there is evidence of renal failure or other contra-indications to these drugs. Their con-comitant use with MTX is routine in patients with rheumatoid arthritis.
• use of another cytotoxic or immunosuppressive drug such as cyclophosphamide, azathioprine, chlorambucil, cyclosporin or trimetoprime currently or in the preceding 6 months.
• current participation in any other drug trial or participation in such a trial in the previous one month.
• serologic evidence of infection with HIV
• biologic potential for pregnancy and not utilizing effective means of contraception
• recently (less than 6 months) diagnosed malignancy
• vitamin B12 deficiency