This paper presents a discussion of Kraton thermoplastic rubber in its application as a raw material for hot melt adhesives. There is a description of the physical and chemical properties of Kraton thermoplastic rubber resulting from its unique molecular structure: a rubbery midblock with two polystyrene endblocks (the simplest molecule); the raw material is thus tough and elastic in addition to being soluble. A two-phase system is formed with the midblock being the continuous phase and the endblocks the dispersive phase. Basic to the formulator's understanding is this two-phase system. Practical starting formulations are given and general principles of Kraton thermoplastic rubber are outlined enabling the formulator to adapt the raw material to his specific needs.