A process for the production and/or purification of the salt of the compound -2-[4-(2-fluorobenzyloxy) benzylamino]propanamide ralfinamide ( Ia), or the respective R-enantiomer ( I ' a), with methanesulfonic acid in the form of the crystalline anhydrous polymorph identified as form A, exhibiting an X-ray powder diffraction pattern (PXRD) having essentially characteristic peaks expressed in degree 2θ at: 6.93;7.80; 9.66; 11.38; 12.04; 13.02; 13.82; 15.60; 16.36; 16.62; 17.52; 17.83; 18.75; 19.35; 19.70; 20.34; 20.69; 21.20; 22.69; 22.95; 23.23; 23.50; 24.80; 25.24; 25.8056; 26.01;27.84; 28.07; 28.55; 29.16; 29.82; 30.77; 31.50; 31.95; 32.38; 33.37; 33.96; 34.61; 34.95; 36.02; 36.46; 37.38; 38.04; 39.66, wherein the content of each of the impurities having genotoxic effect, which consist of one or more (C 1 -C 5) alkylmethanesulfonate(s), is lower than 0.05 ppm and of each of the residual solvents known as potential precursors thereof, which consist of one or more (C 1 -C 5) alkanol(s) or ester(s) thereof with lower alkanoic acid(s), is lower than 6 ppm, characterized in that: (i) the salt is produced or purified by crystallization from a solution in a solvent selected from: a) water, b) a mixture of water with acetone or an aliphatic ketone of 4-5 carbon atoms, and c) acetone, an aliphatic ketone of 4-5 carbon atoms, or a mixture thereof; or (ii) the solid salt containing an undesired amount of the impurities having genotoxic effect and/or of the residual solvents known as potential precursors thereof, is slurried with a solvent selected from: (a) water, (b) a mixture of water with acetone or an aliphatic ketone of 4-5 carbon atoms, and (c) acetone, an aliphatic ketone of 4-5 carbon atoms or a mixture thereof; or (iii) the solid salt containing an undesired amount of the impurities having genotoxic effect and/or of the residual solvents known as potential precursors thereof is exposed to air stream having high degree of relative humidity at a temperature and for a time sufficient to allow the removal of the above said impurities having genotoxic effect and/or of the residual solvents known as potential precursors thereof; and, (iv) when the resulting crystalline form of the so obtained salt is the crystalline hemihydrate pseudopolymorph form identified as form H, exhibiting an X-ray powder diffraction pattern having essentially characteristic peaks expressed in degree 2θ at: 4.09; 7.09; 10.06; 11.64; 12.34; 16.38; 17.00; 17.47; 19.26; 20.11; 20.63; 21.34; 21.97; 23.35; 23.86; 24.12; 25.29; 27.15; 27.61; 28.02; 28.74; 29.62; 30.02; 30.51; 31.29; 31.81; 32.89; 33.35; 33.93; 35.10; 35.39; 35.62; 36.22; 38.91; 39.50; or a mixture thereof with the crystalline anhydrous polymorph form A, (v) said hemihydrate pseudopolymorph form H or the above said mixture thereof is wholly converted into the crystalline anhydrous polymorph form A by removal of the crystallization water on heating. 6.93;7.80; 9.66; 11.38; 12.04; 13.02; 13.82; 15.60; 16.36; 16.62; 17.52; 17.83; 18.75; 19.35; 19.70; 20.34; 20.69; 21.20; 22.69; 22.95; 23.23; 23.50; 24.80; 25.24; 25.8056; 26.01;27.84; 28.07; 28.55; 29.16; 29.82; 30.77; 31.50; 31.95; 32.38; 33.37; 33.96; 34.61; 34.95; 36.02; 36.46; 37.38; 38.04; 39.66, (i) the salt is produced or purified by crystallization from a solution in a solvent selected from: a) water, b) a mixture of water with acetone or an aliphatic ketone of 4-5 carbon atoms, and c) acetone, an aliphatic ketone of 4-5 carbon atoms, or a mixture thereof; or a) water, b) a mixture of water with acetone or an aliphatic ketone of 4-5 carbon atoms, and c) acetone, an aliphatic ketone of 4-5 carbon atoms, or a mixture thereof; or (ii) the solid salt containing an undesired amount of the impurities having genotoxic effect and/or of the residual solvents known as potential precursors thereof, is slurried with a solvent selected from: (a) water, (b) a mixture of water with acetone or an aliphatic ketone of 4-5 carbon atoms, and (c) acetone, an aliphatic ketone of 4-5 carbon atoms or a mixture thereof; or (a) water, (b) a mixture of water with acetone or an aliphatic ketone of 4-5 carbon atoms, and (c) acetone, an aliphatic ketone of 4-5 carbon atoms or a mixture thereof; or (iii) the solid salt containing an undesired amount of the impurities having genotoxic effect and/or of the residual solvents known as potential precursors thereof is exposed to air stream having high degree of relative humidity at a temperature and for a time sufficient to allow the removal of the above said impurities having genotoxic effect and/or of the residual solvents known as potential precursors thereof; and, (iv) when the resulting crystalline form of the so obtained salt is the crystalline hemihydrate pseudopolymorph form identified as form H, exhibiting an X-ray powder diffraction pattern having essentially characteristic peaks expressed in degree 2θ at: 4.09; 7.09; 10.06; 11.64; 12.34; 16.38; 17.00; 17.47; 19.26; 20.11; 20.63; 21.34; 21.97; 23.35; 23.86; 24.12; 25.29; 27.15; 27.61; 28.02; 28.74; 29.62; 30.02; 30.51; 31.29; 31.81; 32.89; 33.35; 33.93; 35.10; 35.39; 35.62; 36.22; 38.91; 39.50; or a mixture thereof with the crystalline anhydrous polymorph form A, 4.09; 7.09; 10.06; 11.64; 12.34; 16.38; 17.00; 17.47; 19.26; 20.11; 20.63; 21.34; 21.97; 23.35; 23.86; 24.12; 25.29; 27.15; 27.61; 28.02; 28.74; 29.62; 30.02; 30.51; 31.29; 31.81; 32.89; 33.35; 33.93; 35.10; 35.39; 35.62; 36.22; 38.91; 39.50; (v) said hemihydrate pseudopolymorph form H or the above said mixture thereof is wholly converted into the crystalline anhydrous polymorph form A by removal of the crystallization water on heating.