A new method that may be useful in the evaluation of renal biopsies is described using fluorescence microscopy on standard hematoxylin and eosin-stained sections of kidney tissue fixed in Hollande's fixative. We describe brightly fluorescing immune complex deposits within glomerular basement membranes and mesangial matrices that correlate well with the results of standard direct immunofluorescence on frozen tissue and electron microscopy. In a blind analysis of 261 consecutive renal biopsies, we determine that this method has diagnostic utility for identification of immune complex glomerulonephritis and significantly extends the usefulness of standard histologic preparations before the use of special stains or procedures.