Barium microangiography is an accepted method for study of the microcirculation. Nonetheless, no method has been previously described for use in mouse models of renal microangiopathy. Using a midline abdominal approach on each of seven anesthetized A/J mice, we inserted a No. 27 lymphangiogram needle into the infrarenal aorta. Using a Harvard pump, the animals were perfused first with 20 ml of 1% glutaraldehyde, then 20 ml of 10% barium sulfate suspension, at 150 mmHg constant pressure. Kidney sections were radiographed onto high-resolution glass plates. Photomicrographs of these images were then enlarged to 5 x 7-inch prints, from which we derived our observations. We observed the normal branching pattern of the renal microcirculation. Mean interlobular artery diameter was 31.89 +/- 2.12 micron SD. Afferent arterioles tapered to a mean preglomerular diameter of 13.55 +/- 1.64 micron. Mean glomerular area was measured to be 2945 +/- 233 sq micron. We have developed a method of renal barium microangiography in the mouse. Desirable features of the technique include its performance on living animals and resolution sufficient to permit objective measurements of microvascular structures.