Cycloalkano[1,2-b]indole-sulphonamides of the formula ##STR1## in which R.sup.1 represents hydrogen, halogen, trifluoromethyl, carboxyl or alkoxycarbonyl, represents a group of the formula --S(O).sub.m R.sup.3, in which R.sup.3 denotes alkyl or aryl, and m denotes one of the numbers 0, 1 or 2, represents a group of the formula ##STR2## in which R.sup.4 and R.sup.5 are identical or different and represent hydrogen, alkyl, aryl, aralkyl or acetyl, represents a group of the formula --OR.sup.6, in which R.sup.6 denotes hydrogen, alkyl, aryl, aralkyl, alkyl-SO.sub.2 --, aryl--SO.sub.2 --, aralkyl--SO.sub.2 -- or trifluoromethyl, or represents alkyl, alkenyl or cycloalkyl, each of which is optionally substituted by carboxyl, alkoxycarbonyl, halogen, hydroxyl, alkoxy, alkylthio or cyano, R.sup.2 represents aryl which is optionally substituted up to 5 times by halogen, cyano, trifluoromethyl, trifluoromethoxy, trifluoromethylthio, alkyl, carboxyalkyl, alkoxycarbonylalkyl, alkoxy, alkylthio, hydroxyl, carboxyl, alkoxycarbonyl, phenyl, phenoxy, benzyloxy, benzylthio or a group of the formula ##STR3## in which R.sup.4 and R.sup.5 have the abovementioned meaning, x represents the number 1, 2 or 3, and y represents the number 0 or 1, where appropriate in an isomeric form, and their salts are disclosed. These compounds are useful to inhibit platelet aggregation and to antagonize thromboxane A.sub.2.