The present invention relates to the new 15-membered ketoazalides from the class of 6-O-methyl-8a-aza-8a-homo-and 6-O-methyl-9a-aza-9a-homoerythromycin A with the general formula (I) ##STR1## wherein A represents NH group and B at the same time represents C.dbd.O group, orA represents C.dbd.O group and B at the same time represents NH group,R.sup.1 represents OH group, L-cladinosyl group of the formula (II) ##STR2## or together with R.sup.2 represents ketone, R.sup.2 represents hydrogen or together with R.sup.1 represents ketone,R.sup.3 represents hydrogen or C.sub.1 -C.sub.4 alkanoyl group,to intermediates and a process for their preparation, to their pharmaceutically acceptable addition salts with inorganic or organic acids, to the process for the preparation of pharmaceutical compositions, as well as to the use of pharmaceutical compositions for treating bacterial infections.