In the title compound, C(5)H(8)N(3) (+)·C(4)H(5)O(4) (-), the pyridine N atom of the 3,4-diamino-pyridine mol-ecule is protonated. The protonated N atom participates in an N-H⋯O hydrogen bond to a succinate O atom of the singly deprotonated succinate anion. Each of the two amino groups are hydrogen-bonded to the O atoms of two different sets of succinate groups.. The crystal structure is furthe...