Student interest is often stimulated by naturally occurring compounds that possess biological activity.  One example known for many years, but not often described in introductory organic textbooks, is nepetalactone: a monoterpene-derived fused bicyclic enol lactone.  Recognized mostly as feline stimulants, the two major diastereomers of nepetalactone found in N. cataria also possess the ability to repel some insect species and their potential as biological control agents have recently been investigated.  To independently establish the essential oil composition of N. cataria our students steam distilled the organic volatiles from seven brands of commercial catnip to obtain 20-40 mg of viscous oil from 10 g of dried plant material.  Analysis by GC-MS and ¹H/¹³C NMR spectroscopy, in comparison with reported spectral data, revealed that five samples contained either the cis-fused lactone (1) or the trans-fused lactone (2) as the predominant steam-volatile product, along with 1-8% of the other diastereomer.  A sixth sample contained a mixture of 1, 2 (with a 1:2 ratio of 90:10) and significant amounts of several other substances.  A seventh, spurious sample contained predominantly menthol with no detectable amounts of nepetalactone.  Lactones 1 and 2 are separable by TLC and visualized using standard methods; thus, even without access to spectral data each student can analyze their own sample, and by co-spotting their sample along with those of other students they readily establish that most commercial sources of catnip contain one of two possible compounds (1 or 2) as the single, predominant steam-volatile product.