This chapter reviews azaspiracids (AZA) to distinguish those analogues that are formed by the microalgae themselves from those that are formed by biotransformation or by chemical modification during extraction or sample treatment. It describes chemical characteristics such as solubility and pH and thermal stability, and discusses methods for discovery of AZA analogues including bioassays and chemical techniques. The chapter provides methodology for detection and quantitation with consideration of quality control in routine analytical settings. In addition to the biotransformation and chemical reactions described earlier, chemical characteristics of AZAs contribute to the overall understanding of the behavior in the environment and in isolation studies, as well as their impact on biological systems. To date, no formal solubility studies have been reported for AZAs, most likely due to the limited availability of the toxins. Thermal stability has been mostly studied for AZAs in Shellfish tissue.