1-Substituted pyrazole-5-ones of the formula ##SPC1##And pharmaceutically acceptable, nontoxic salts thereof, whereinR is hydrogen or amino;R.sup.1 is hydrogen, alkyl, alkenyl, unsubstituted or substituted aryl or unsubstituted or substituted aralky;X isA. ethylene, ethylene wherein 1 hydrogen atom on one of the carbon atoms is substituted by alkyl of 1 to 4 carbon atoms, ethylene wherein 1 hydrogen atom on each of the two carbon atoms is substituted by alkyl of 1 to 4 carbon atoms or said ethylene which is linked to R.sup.2 via an oxygen or sulphur atom;B. propenyl, propenyl wherein 1 hydrogen atom on one, two or three of the carbon atoms is substituted by alkyl of 1 to 4 carbon atoms, said propenyl being linked to the N.sup.1 atom of the pyrazol ring via its methylene moiety; orC. methylene;Provided that when X is methylene, R.sup.1 is not hydrogen if R is amino;R.sup.2 is aryl unsubstituted or substituted by:A. 1 or 2 of the same or different substituents selected from the group consisting of halogen, trifluoromethyl, alkyl of 1 to 8 carbon atoms, alkenyl of 2 to 8 carbon atoms and lower alkoxy;B. cycloalkyl of 5, 6 or 7 carbon atoms of cycloalkenyl of 5, 6 or 7 carbon atoms,C. alkylamino, dialkylamino, cyano, trifluoromethoxy, nitro, carbamoyl, alkylcarbamoyl, dialkylcarbamoyl, or said carbamoyl wherein the nitrogen atom is a member of a heterocyclic ring, sulphamyl, alkylsulphamyl, dialkylsulphamyl, or said sulphamyl wherein the nitrogen is a member of a heterocyclic ring, or --SO.sub.n alkyl wherein n is 0, 1 or 2;D. alkylamino, dialkylamino, cyano, trifluoromethoxy, nitro, carbamoyl, alkylcarbamoyl, dialkylcarbamoyl, or said carbamoyl wherein the nitrogen atom is a member of a heterocyclic ring, sulphamyl, alkylsulphamyl, dialkylsulphamyl or said sulphamyl wherein the nitrogen is a member of a heterocyclic ring, or --SO.sub.n -- alkyl wherein n is 0, 1 or 2, and 1 or 2 of the same or different substituents selected from the group consisting of alkyl, alkenyl, alkoxy, halogen, and trifluoromethyl; orE. a fused, saturated or unsaturated 5-, 6-, or 7-membered ring or said ring containing 1 or 2 oxygen or sulphur atoms;Are useful for their diuretic, saluretic, antihypertensive and antithrombotic effects.