Background: The purpose of this study was to evaluate whether a random urinary protein / creatinine ratio is a clinically useful predictor of significant proteinuria (300 mg/24 hr) instead of 24- hours urine protein, among women with suspected preeclampsia. Methods: Women with suspected preeclampsia and gestational age of 20 weeks were included in a prospective study. Patients with chronic hypertension, diabetes mellitus, or preexisting renal disease were excluded. Protein/ creatinine ratio was obtained before 24-hours urine collection. Positive and negative predictive values and sensitivity and specificity of the protein/creatinine ratio for significant proteinuria (300 mg) were calculated, based on 24-hours urine total protein. Results: 100 women were evaluated totally. Mean maternal and gestational ages were 27.3 years and 33.26 weeks, respectively.73% of cases had significant proteinuria based on 24-hours urine collection. Good correlations were found between the protein/creatinine ratio in random urine samples and both the 24-hours urine protein excretion and the 24- hours urine protein/creatinine ratio in patients with mild preeclampsia (r=0.484, P<0.0001, and r=0.345, P<0.0001, respectively) .Receiver operator characteristic (ROC) analysis revealed an area under the curve of 0.944. The best cutoff value was of >0.18 which yields a sensitivity of 86.3%, a specificity of 100%, with a positive predictive value of 100%, and a negative predictive value of 73%. Conclusion: The random urinary protein –to- creatinine (P: C) ratio is strongly associated with the 24-hours total protein excretion. A cutoff value of > 0.18 is a good predictor of significant proteinuria .P: C ratio could replace the 24- hours urine collection as a simpler, faster, and more accurate method for the diagnosis of significant proteinuria. Key words: Preeclampsia, significant proteinuria, protein / creatinine (P: C) ratio, 24- hours urine total protein level