4-(3-Carb-oxy-1-ethyl-6-fluoro-4-oxo-1,4-dihydro-7-quinol-yl)-1-methyl-piper-azin-ium picrate.

The pefloxacinium cation of the title salt, C(17)H(21)FN(3)O(3) (+)·C(6)H(2)N(3)O(7) (-), is composed of an essentially planar quinoline ring system [maximum deviation = 0.021 (2) Å] and a piperazine ring, which adopts a chair conformation. In the picrate anion, the two O atoms of one of the o-NO(2) groups are disordered over two positions, with an occupancy ratio of 0.56 (4):0.44 (4). In the crystal structure, cations and anions are connected by inter-molecular N-H⋯O, O-H⋯O, C-H⋯O and C-H⋯F hydrogen bonds, forming a three-dimensional network. In addition, π-π inter-actions between the pyridine rings and between the benzene rings of the anions, with centroid-centroid distances of 3.6103 (12) and 3.5298 (11) Å, respectively, are observed.