Ten dogs presenting mild chronic renal failure and hypertension after 27 months of uninephrectomy, during which they received a high sodium and high protein diet, were divided in two groups (n = 5) and followed for 15 months. The same diet was maintained and one of the groups received cicaprost treatment. The animals were periodically tested for biochemical and clinical parameters, and at months 0, 3, 6, and 15, glomerular filtration rate and renal plasma flow (RPF) were measured. Renal biopsies were made after 6 months of follow-up. Control group showed a higher thickening of pre- and intraglomerular portions of arteriolar vessels and an enhancement of mesangial matrix when compared with the treated group. Cicaprost also induced a significant elevation in RPF and a significant decrease in filtration fraction. All these findings suggest that cicaprost, an oral stable prostaglandin I2 analog, could have a protective renal effect in this experimental model.