This chapter lists the CAS registry number, chemical structure, chemical abstract (CA) index name, other chemical names, Merck Index number, chemical/dye class, synthesis procedure, molecular formula, and molecular weight of the Alexa Fluor 790 carboxylic acid succinimidyl ester. Other properties listed for this fluorescent dye include the physical form, solubility, melting point, boiling point, pKa, absorption maxima, emission maxima, molar extinction coefficient and quantum yield. The chapter also includes references on the use and properties of Alexa Fluor 790 carboxylic acid succinimidyl ester. It presents a list of imaging/labeling applications and biological/medical applications of Alexa Fluor 790 carboxylic acid succinimidyl ester.