objective: to evaluate the usefulness of vaginal fluid creatinine concentration as a diagnostic method for premature rupture of membranes. setting: delivery room at "maternidad concepcion palacios", caracas. methods: creatinine was determined in vaginal fluid of 120 healthy women, with 22 weeks or more of gestation, dividided into 2 groups, one with rupture of membranes (group a) and with out it (group b). results: in the group a patients, the average creatinine concentration was 0,72 ± 0,49 mg/dl, with extremes of 0.10 and 1.80. in the group b creatinine was not found in the vaginal fluid. sensibility and specificity was 100 %. conclusion: vaginal fluid creatinine concentration higher than 0.1 mg/dl, is a reliable marker as a diagnostic method for premature rupture of membranes.