Introduction Proteinuria (⩾300 mg/24 hs) is one of the parameters that define preeclampsia. According to the literature, proteinuria concentration ⩾two or five grams defines severe preeclampsia, and massive proteinuria is defined by at least 10 g. Objective To identify and classify the severity of proteinuria in preeclamptic pregnant women. Methods Were studied 101 preeclamptic women, who received obstetric care during the year of 2015 at the Maternity of the Botucatu Medical School Hospital, Botucatu, SP, Brazil. Proteinuria was classified as mild (300–1999 g), two severe grades (2000–4999 g and ⩾5000 g) and massive (⩾10,000). The following parameters were evaluated: demographic [age, race, marital status] and obstetric characteristics [parity, gestational age at pregnancy resolution, forms of preeclampsia (superimposed or not upon chronic hypertension, early or late onset, mild or severe, and type of delivery). Results In the studied population predominated the age between 20 and 35 years old, white race and stable union. Parity was similar between primiparous and multiparous, with 41.6% of prematurity and 69.3% of caesarean section. In the characterization of pre-eclampsia predominated pure (80.2%), severe (73.3%) and late (81.2%) forms. Among the parameters of severity, predominated hypertensive crisis (49.5%), proteinuria (33.7%) and imminent eclampsia (22.8%). The median values and range of proteinuria were 900 mg/24 h (300–36,014 mg), and classified as mild (66.4%) or severe ⩾2000 mg (33.6%). Considering severe (⩾5000 mg) and massive proteinuria the values were 22.7% and 10.8%, respectively. Discussion Proteinuria was a parameter of severity in one third of cases of preeclampsia, with 10.8% of massive grade. In our service, one year of follow-up of pregnant women, who developed severe preeclampsia showed persistence of proteinuria and/or albuminuria in 27% of patients. However, there is no literature indication of which proteinuria concentration should be an indicator for gestation interruption in order to avoid future impairment of renal function of these women.