Benzenesulfonylureas and -thioureas of the formula I ##STR1## where R(1) is H or (fluoro)methyl, R(2) is H, Hal or (fluoro) (mercapto) alk (oxy) yl, E is O or S; Y is --[CR(3).sub.2 ]n-, where R(3)=H or alkyl and n=1-4, X is H, Hal or alkyl and Z is Hal, NO.sub.2 or alk(yl)oxy, are described.The compounds I are used for treatment of disturbances in cardiac rhythm and prevention of sudden cardiac death caused by arrhythmia, and can therefore be used as antiarrhythmics. They are particularly suitable for those cases where arrhythmias are a consequence of a narrowing of a coronary vessel, such as angina pectoris or acute cardiac infarction.