Abstract: The prognosis of Systemic Lupus Erythematosus depends partly on renal involvement. Lupus nephritis has evolved from a frequently terminal process such as type IV lupus nephritis according to WHO classification to one in which a fairly normal quality of life and good outcome are possible. The aim of this study was to try to predict the short-term outcome of type IV lupus nephritis by looking at the disease variables before treatment. A way to achieve this goal is to look at patients with bad and good outcome to determine if some sign or symptom, or a combination of them, will differentiate the two groups. For this purpose 73 variables were analyzed by the computer assisted Classification and Regression Tree Method in'163 patients with SLE nephritis. The final tree had 12 terminal nodes. The short outcome of renal involvement was related to systolic blood pressure, C3 and C4 complement levels, level of proteinuria, creatinine clearance, ESR, and monocyte infiltration and tubular atrophy on renal biopsy. The prognosis is bad if the systolic blood pressure is more than 140 mm/hg plus monocyte infiltration on renal sample and daily urine protein excretion above 3 gr. If the blood pressure is normal but the C3 and C4 complement is low and tubular atrophy is detected in renal specimen, the prognosis is also bad. The prognosis is bad if the C4 complement is low and the daily urine protein excretion is more than 3 g, the creatinine clearance is low plus erythrocyte sedimentation rate more than 50 mm/hour. The short-term prognosis is bad in the presence of tubular atrophy and low level of C3.