The active pharmacological compound in a street drug sample is not volatile at ambient temperatures and is probably not what triggers and alert response from a trained drug dog. Improved understanding of the ‘signature’ odor characteristics of illicit street drugs offers insight into the detection and some fundamental mechanisms of canine and human olfaction. Signature odor and smell of a drug is typically caused by compounds present as very low concentrations and are not targeted in forensic analytical methods. Forensic analytical methods focus on active compounds or their breakdown intermediates, which may not elicit any olfactory response or be only a ‘background’ to a handful of high odor impact compounds. It has been our experience that it is typically the handful of compounds present at very low concentrations that impart the overall characteristic smell of a sample. Our working hypothesis is that a small number of volatile and semi-volatile compounds present in very low concentrations and associated with very low odor detection thresholds cause the characteristic smell of a drug. These high odor impact compounds are not being used to manufacture surrogate training scents used in training forensic canines. This omission could explain why these surrogate scents are generally not effective. This information could lead to increased understanding of what drug detection canines are using as the signature odor of street drugs. In this thesis, headspace solid phase microextraction and multidimensional gas chromatography-mass spectrometry and simultaneous olfactometry is being used for collection, separation, and identification of volatile organic compounds (VOCs) emitted from marijuana, cocaine, and heroin. Compounds with significant odor impact, as detected by human nose did not always coincide with chemical concentration of VOCs emitted from the drug. A comparison of commercially available pseudo scent training aides versus real drug odors showed many inconsistencies. Research is warranted to continue linking smell of ‘signature’ drug aromas towards improved understanding of human and canine drug detection and olfaction.