Background: 24-h urinary pr is a standard way to diagnose lupus nephritis. Assessment of Pr/Cr ratio in morning spot urine is a valuable method in diabetic patients but it has no use in SLE patients routinely. In this study Pr/Cr ratio in spot urine was compared with 24-h urine Pr. If they have valuable correlation, we can use this test instead of 24-h urinary Pr. The aim of this study was to evaluate the correlation of spot urine protein-creatinine ratio for prediction of significant proteinuria (> or = 300 mg/24 h) in patients with systemic lupus erythematous. Methods: A cross-section study was conducted in 74 hospitalized women with systemic lupus erythematous. The correlation between Prot/Cr in first morning urine specimens and urinary protein excretion were analyzed in 24-h collections. Findings: Correlation between Prot/Cr ratio in spot morning urine specimens and urinary protein excretion in 24-h collections was significant. Conclusion: A high correlation and precision of agreement were demonstrated between the two methods of assessment proteinuria in lupus patients. The difference between the two methods was less than the biological variability in the protein excretion and its measurement, enabling the methods to be used interchangeably creatinine ratio in spot morning urine samples is a precise indicator of proteinuria in patients with lupus nephritis and represents a simple and inexpensive procedure in establishing severity of proteinuria in patients with systemic lupus erythematous. Key words: Systemic Lupus Erythematous, 24-h urine protein measurement, protein / creatinine ratio.