The invention comprises compounds of the formula <FORM:0821161/IV (a)/1> wherein the pyridine nucleus may be substituted by an alkyl radical containing 1-10 carbon atoms or by a second acetal group, R1 and R2 are the residues of an aliphatic or cycloaliphatic alcohol, X1 is an alkyl, alkenyl, aralkyl or aryl radical, the aryl and aralkyl radicals optionally bearing halogen, nitro or amino substituents, and X2 is the anion of an acid, and their preparation by reacting 1 mol. of a pyridine acetal with 1 mol. of a quaternizing component, heating the reaction mixture for several hours to a temperature of 45-100 DEG C. and isolating the product.  The compounds may also be made by converting a quaternary pyridinium aldehyde into its acetal. Preferably R1 and R2 are the residues of an aliphatic alcohol of 1-4 carbon atoms.  The compounds are used therapeutically in the treatment of rheumatic diseases and in cosmetic preparations. Examples describe the preparation of N-methyl-pyridinium-3-aldehyde dimethyl acetal iodide, N-methyl-pyridinium-3-aldehyde diisobutyl acetal iodide, N-(2 : 4-dinitrophenyl) - pyridinium - 3 - aldehyde dimethyl acetal chloride, N - methyl - pyridinium-4-aldehyde dimethyl acetal iodide, N-methylpyridinium - 2 : 6 - dialdehyde tetramethyl acetal iodide, N-methyl-pyridinium-4-aldehyde isopropyl acetal iodide, N-ethyl-pyridinium-3-aldehyde dimethyl acetal iodide, N-ethyl-pyridinium - 3 - aldehyde dimethyl acetal bromide, N - propyl - pyridinium - 3 - aldehyde dimethyl acetal iodide, N - methyl - pyridinium - 3 - aldehyde dimethyl acetal iodide and N-benzyl-pyridinium-3-aldehyde dimethyl acetal iodide.ALSO:Pharmaceutical and cosmetic preparations contain as an active constituent a pyridinium compound of the formula <FORM:0821161/VI/1> wherein the pyridine nucleus is optionally substituted by an alkyl radical of 1-10 carbon atoms or by a second acetal group, R1 and R2 are the residues of an aliphatic or cycloaliphatic alcohol, X1 is an alkyl or alkenyl radical or an aralkyl or aryl radical optionally bearing halogen, nitro or amino substituents, and X2 is the anion of an acid. Preferably R1 and R2 are the residues of an aliphatic alcohol of 1-4 carbon atoms, but they may also be residues of a cycloaliphatic alcohol such as menthol, X1 is an alkyl or alkenyl radical of 1-4 carbon atoms and X2 is a halogen atom, e.g. iodine (see Group IV (b)).  The compounds may be used to promote blood circulation and for the treatment of rheumatic diseases, suitably in the form of alcoholic solutions containing 0.01 to 10%, more preferably 0.1 to 1% of active compound, isopropyl alcohol being a suitable solvent.  The compounds may also be used cosmetically in hair creams and skin oils and for treatment of the gums.  A hair cream formulation comprises stearin, glycerine, potassium and sodium hydroxide, butyl stearate, water and N-methyl-pyridinium-4-aldehyde dimethyl acetal iodide; a skin oil comprises castor oil, ethanol and N-methyl-pyridinium-3-aldehyde dibenzyl acetal iodide; a dentifrice comprises glycerine, water, silica gel, N - methyl - 6 - methyl - pyridinium - 2-aldehyde diethyl acetal iodide, peppermint oil, magnesium hydrogen phosphate, calcium hydrogen phosphate and calcium phosphate, and a gargle comprises tinctures of myrrh, iris root and quillaia, ethereal oil, aqueous ethanol and N-methyl-pyridinium-4-aldehyde dimethyl acetal iodide.