A luminescence immunoassay (LIA) has been developed utilizing the chemiluminescent luminol reaction with heme as catalyst. Rabbit antibody against human serum albumin was quantitated in antigen coated plastic tubes using commercially available goat anti-rabbit IgG conjugated to horseradish peroxidase which was the source of heme. The measurable range of antibody is considerably wider by LIA than by enzyme immunoassays. The time to develop and measure activity is short and constant which makes LIA suitable for automation. In its present form, LIA is slightly less sensitive but has better day-to-day reproducibility than corresponding enzymes immunoassays.