Altered renal function is an essential component of the pathophysiological process in preeclampsia. The kidneys play a significant part in the turnover of most low molecular weight substances such as creatinine, urate and cystatin C. The present work was undertaken to investigate if the serum levels of these components are altered in characteristic ways in preeclampsia, and can be used to assist in the diagnosis of this condition. The serum levels were therefore determined in samples from 100 healthy women at term as well as in 45 samples of patients with preeclampsia (diastolic blood pressure >90 mmHg; urinary albumin excretion >300 mgL(-1)). The levels of all three components were significantly higher in samples from preeclamptic patients with the mean+SD being 1.55+/-0.29 vs. 1.05+/-0.19 mg L(-1) for cystatin C, 70+/-23 vs. 56+/-9.7 micromol L(-1) for creatinine, and 413+/-128 vs. 305+/-61 micromol L(-1) for urate. Receiver operating characteristic analysis demonstrated that the serum level of cystatin C had a superior diagnostic accuracy for preeclampsia compared to those of serum urate and creatinine and that the diagnostic accuracy of serum urate was better than that of serum creatinine.