Preeclampsia remains a leading cause of maternal and fetal morbidity and mortality but has an unknown etiology. Women with elevated baseline blood pressure have an increased risk of this disorder. We hypothesized that BPH/5 mice, an inbred mouse strain with mildly elevated blood pressure, would develop a pregnancy-induced hypertensive syndrome. Nonpregnant female BPH/5 and C57BL/6 mice underwent thoracic aortic implantation of telemeters. After 7 days of recovery and 5 days of baseline mean arterial blood pressure (MAP) recording, strain-matched timed matings were carried out. MAP was recorded continuously during pregnancy and for 1 week after birth. In separate mice in metabolic cages, urinary protein was tracked, followed by renal histological analysis. Before pregnancy, the BPH/5 strain had elevated baseline MAP compared with the C57BL/6 strain, but both strains had similar total urinary protein levels and renal histology. MAP remained stable in both groups during the first 2 weeks of pregnancy. However, at the start of the last trimester, MAP began to rise further in the BPH/5 mice; it rose to peak levels just before delivery and returned to prepregnancy levels by 2 days after delivery. This was accompanied by late-gestational proteinuria and progressive glomerulosclerosis. No changes were observed in the C57BL/6 group except for a small decrease in MAP at mid gestation. The BPH/5 group delivered significantly smaller litters despite normal numbers of fetuses early in gestation, and longitudinal ultrasound studies documented fetal demise before the onset of hypertension and renal disease. This is the first report of an animal model that spontaneously develops a syndrome that bears close resemblance to preeclampsia, and it should have an impact on our understanding of the pathophysiology of this disorder.