Publisher Summary This chapter deals with the chemistry of aminoisoxazoles(AI), which is a subsection of isoxazole chemistry. The available amino group changes distinctly the properties and reactivity of the isoxazole ring, and some reactions and rearrangements that are unusual in isoxazole chemistry become typical. An amino group is convenient in combinatorial chemistry and facilitates the use of these compounds in modern drug discovery. The studies on AI have been mainly concerned with the biological activities and the preparation of fused heterocyclic systems, such as isoxazolopyridines, isoxazolopyrimidines, and isoxazolodiazepines. AI-based condensed heterocyclic systems are more biologically promising than AI themselves. Indeed, AI derivatives possess cytostatic, antibacterial, herbicidal, immunological, hypocholesterolemic, and anticonvulsant activities among other activities.