1. The renal blood flow distribution has been studied by the Xe washout method in nineteen patients undergoing routine left-sided cardiac catheterization.
2. It was found that there were two separate groups, one in which the washout curve could be analysed by curve stripping into four exponentials, and one in which only three could be detected.
3. The mean cardiac output was found to be lower in the three-component group, whereas the mean glomerular filtration rate did not differ significantly between the two groups.
4. In the four-component group but not in the three-component group, significant linear correlations were detected between cardiac output and glomerular filtration rate, and between glomerular filtration rate and intrarenal blood flow distribution.
5. One suggestion was that the three component distribution of renal blood flow was associated with increasing renal autoregulation and the maintenance of renal function in the presence of a low cardiac output.
6. A second suggestion was that the differences between the three- and four-component group were primarily due to the more intensive diuretic therapy given to the patients in the three-component group.