A chemiluminescence immunoassay has been developed for the measurement of albumin concentrations in human urine, as an indicator of diabetic nephropathy. The assay involved competition between analyte albumin and an acridinium ester labelled albumin tracer for binding to a rabbit (anti-human albumin) antibody. Immune complexes were separated using sheep (anti-rabbit immunoglobulin G) antibodies coupled to paramagnetic particles. The total incubation time was ninety minutes at room temperature followed by sedimentation and washing of the solid-phase using a magnetic rack. Chemiluminescence emission was quantified rapidly (2 s) using a commercially available luminometer. The assay was sufficiently sensitive (10 ng/ml) for the detection of microalbuminuria with the advantages of rapidity and use of stable reagents. The assay correlated well with both RIA and rate nephelometry.