Abstract: The invention relates to halo derivatives of 9a-N-(N?-arylcarbamoyl)- and 9a-N-(N?-arylthiocarbamoyl)-9-deoxo-9a-aza-9a-homoerythromycin A of the general formula (I) wherein R has the meaning of a substituted aryl group of the formula (II) wherein substituents a, b, c, d and e are the same or different and at least one of them has the meaning of halo, a (C1-C6)haloalkyl or a (C1-C6)haloalkoxy group, whereas the remaining ones have the meaning of hydrogen, halo, a (C1-C6)alkyl or a (C1-C6)alkoxy group, and X has the meaning of oxygen or sulfur, and pharmaceutically acceptable addition salts thereof with inorganic or organic acids, to a process for their preparation, to a process for the preparation of pharmaceutical compositions comprising them and to the use of these pharmaceutical compositions for the treatment or prevention of bacterial infections.