We conducted an immunohistochemical analysis to investigate the presence of monocyte chemoattractant protein-1 (MCP-1) in normal and diseased human kidneys and the correlation with infiltration of macrophages. A total of 50 renal biopsies were classified according to pathologic diagnosis. The distribution as well as the intensity of MCP-1 staining, and infiltration by CD68+ macrophages were evaluated in diseased versus normal kidneys. Weak staining of MCP-1 was detected in normal renal tissue, especially in tubular epithelial cells. Significant alterations in MCP-1 staining were observed in a number of diseases, in which the intensity of MCP-1 staining rather than the distribution of MCP-1-positive cells was higher. In membranous nephropathy, IgA nephropathy, and glomerulosclerosis, an association was found between the intensity of MCP-1 staining in tubular epithelial cells and interstitial infiltration of macrophages. The glomeruli in membranous nephropathy showed a stronger intensity of MCP-1 staining particularly in the glomerular visceral epithelial cells. The glomerular MCP-1 staining did not correlate significantly with the number of macrophages in the glomeruli. In conclusion, we describe increased cellular staining for MCP-1 in diseased human renal tissue, especially by tubular epithelial cells. Our observations suggest, complementary to in vitro and in vivo observations made by us and others, that specific roles may be played by MCP-1 in physiological and inflammatory processes in the kidney.