Acetylcholine picrate, C7H16NO2+.C6H2N3-O7-, Mr = 374.3, orthorhombic, Pbca, at 105 K: a = 18.799 (4), b = 7.726 (2), c = 22.878 (4) A, V = 3323 (2) A3, Z = 8, Dm(295 K, flotation) = 1.44, D chi(105 K) = 1.496 Mg m-3, mu(Mo K alpha) = 0.120 mm-1, F(000) = 1568, m.p. (hot-stage microscope) 381-382 K, R = 0.048 for 1049 observed [I greater than or equal to 3.0 sigma(I)] reflections. Methoxycarbonylcholine picrate hemihydrate, C7H16NO3+.C6H2N3O7-.1/2H2O, Mr = 399.3, monoclinic, P2/n, at 105 K: a = 11.337 (16), b = 7.279 (2), c = 21.424 (13) A, beta = 103.01 (7) degrees, V = 1723 (4) A3, Z = 4, Dm(295 K, flotation) = 1.49, D chi(105 K) = 1.539 Mg m-3, mu(Mo K alpha) = 0.126 mm-1, F(000) = 836, m.p. (hot-stage microscope) 391-391.5 K, R = 0.033 for 6359 observed [I greater than or equal to 3.0 sigma(I)] reflections. The acetylcholine ion as well as the methoxycarbonylcholine ion have as first neighbours a great number of oxygen atoms. Contacts to the quaternary ammonium group do not seem to be more important than contacts to the acetyl or methoxy-carbonyl moieties. No direct contacts between aromatic rings and quaternary ammonium groups are found.