We offer a competitive receptor binding assay kit for the site 5 sodium channel ligands brevetoxin or ciguatoxin. Brevetoxins and ciguatoxins are produced by marine algae that are then consumed by commercially important shellfish or fish. When consumed, brevetoxins and ciguatoxins can cause Neurotoxic Shellfish Poisoning (1) or Ciguatera Fish Poisoning (2), respectively. Our test kit can detect and quantify either of these toxins (3-6). The kit can be used as a screening or quantitative tool with analyses completed in less than 2 hours after extraction. This methodology is faster and less expensive than LC/MS or N2A cell-based methods. Each kit is capable of analyzing from 5 to 8 samples in dilution series (quantitative mode) or up to 40 samples at a single dilution in duplicate (qualitative mode).