N‐Vinyl pyrrolidone (VP) and N‐vinyl caprolactam (VCAP) are five and seven‐membered lactam compounds linked through the nitrogen atom to a polymerizable carbon–carbon double bond. This chapter deals with the physical properties of VP and VCAP, followed by their molecular structures, and finally elaborates on the organic reactions made possible through these physical, chemical, and structural properties. The vast majority of small molecule organic transformations originate from the moderately polarized and electron rich C═C double bond in VP and VCAP. The chapter describes a diverse array of organic reactions involving the C═C double bond of VP and VCAP, categorized by the constructions of carbon–carbon, carbon–nitrogen, carbon–oxygen, carbon–silicon, carbon‐phosphorous, carbon–sulfur bonds. It also describes the C–C bond formation via the nucleophilic substitution of an alkyl group at the α‐carbon of the lactam ring. Double α‐acylation is feasible and hence a mixture of mono‐, di‐acylated VP may be obtained.