A crystallization study was undertaken to relate the structure of small amines to the zeolite product obtained. At SiO2/Al2O3 = 200, certain noncyclic amines (some not previously recognized) were specific for the formation of 10-ring zeolites, e.g., ZSM-22 and ZSM-23. For example, ethylmethylamine and diethylamine yielded highly crystalline ZSM-22, while ethylamine and isopropylamine yielded ZSM-23. Consistent with their larger size, cyclic amines such as piperazine produced the 12-ring pore system, ZSM-12. At lower SiO2/Al2O3 ratios (40), a different set of zeolites was obtained, as expected, ZSM-35 and MCM-22. Again, a specific relationship was observed between the amine employed and the zeolite obtained. In both SiO2/Al2O3 regimes, several amines played non-structure-specific pore- and pH-stabilizing roles and yielded ZSM-5. With relatively few exceptions, the zeolite products were fully porefilled with amine and low in Na (Na/Al < 1). Computer simulations confirmed a pore-stabilizing role for both structure-specific and non-structure-specific amines. At the same time, among structure-specific ("structure-directing") amines, they showed that the interaction energy differences between alternative amine-pore combinations were often quite small (0.5-2.0 kcal/mol, for example). Nevertheless, the changes in amine-pore interaction energies for this group of amines consistently tracked the changes in zeolite products observed.