Abstract: Present research aim is to determine whether quantitative measurements of 8 and 12 h urine protein vs. 24 h sample are accurate in diagnosing preeclampsia and in differentiating mild from severe disease. The longitudinal-experimental method conducted on 60 preeclamptic women (30 patients with mild preeclampsia and 30 patients with severe preeclampsia). The 8, 12 and 24 h urine protein were compared and results were analyzed by the SPSS-10 statistical software. There was a significant relation between diagnosis of preeclampsia and the amounts of 8, 12 and 24 h urine protein (p = 0.000). The relation of systolic (p = 0.000) and diastolic (p = 0.001) blood pressure with severity of preeclampsia was significant. There was significant relation between gestational age and severity of disease (p = 0.012) but the relation of gestational age with parity, gravidity, serum creatinine level, urine volume and urine creatinine level was not significant (p>0.05). Determining total protein of 8 and 12 h urine samples can be a good alternative for 24 h urine protein measurement. This would lead to a faster diagnosis for severe preeclampsia, earlier treatment and consequently reducing morbidity and mortality of mother and fetus/infant.