Serum samples from 73 cases of Systemic lupus erythematosus (SLE) were studied for proteins, immunoglobulins, complement components and anti-nuclear antibodies. In fresh cases of SLE, low serum albumin, high alpha-1, alpha-2, and gamma-globulins were found. Marked elevation of serum levels of IgG was found at the time of diagnosis, but this returned to normal after regular treatment. Over 71% of SLE had serum levels of C3 and C4 lower than normal (mean - 2SD). The more severe the disease, the lower the serum levels of these two components of complement. Fluorescent anti-nuclear antibody (FANA) was found in 98.6% of the cases studied. Most (85.1%) cases and anti-double stranded deoxyribonucleic acid (anti-ds DNA) antibody levels higher than normal control (mean + 2 SD). We may conclude that FANA, C3, C4 and anti-ds DNA anatibody are immunological parameters sensitive in the early diagnosis of SLE. FANA is the most sensitive, and can be used as a screening test in SLE. The serum C3 and C4 levels correlate well with the severity of the disease.