In the title compound, C(5)H(7)N(2) (+)·C(7)H(5)O(3) (-), the carboxyl-ate mean plane of the 4-hydroxy-benzoate anion is twisted by 8.78 (5)° from the attached ring. The cations and anions are linked via O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds, forming a three-dimensional network. In addition, π-π inter-actions involving the benzene and pyridinium rings, with centroid-centroid distances of 3.5500 (6) and 3.6594 (6) Å, are observed.
* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.