Our ability to smell relies on odorant receptors (ORs) in the olfactory sensory neurons of the olfactory epithelium. Mammalian ORs are seven transmembrane G-protein-coupled receptors that are expressed on the cilia membrane at the tip of the dendrite in the olfactory sensory neurons. Each OR is specialized to bind specific features of odorant molecules. ORs represent the largest gene superfamily in the mammalian genome and account for the diversity of odors that we can detect, yet it is not known how the olfactory system encodes an olfactory percept. Understanding how a range of perceptual qualities regarding tens of thousands of odorants interacting with hundreds of ORs requires an assay that can probe a large number of single odorant-single receptor interactions. Heterologous expression systems allow us to probe the interaction of a single odorant with a single receptor. The discovery of chaperone proteins, RTP1 and RTP2, that enhance the cell-surface expression of ORs allowed us to develop a high throughput screening system for ORs. By describing the large number of OR-ligand interactions, we hope to be able to relate properties of odorants and the ORs.