Conjugated meningococcal capsular saccharides will be introduced into immunization schedules in the near future, but the phenomenon of “carrier suppression” must first be addressed, particularly where multiple conjugates are to be used. It has been found that diphtheria toxoid and its derivatives (such as CRM197) can safely be used as the carrier protein, even where multiple meningococcal conjugates are administered at the same time and where a patient has previously been exposed to the carrier protein, either in the form of a previous immunogen (e.g. in a DTP vaccine) or as a previous carrier protein (e.g. in a Hib or pneumococcal conjugate vaccine). The invention provides a method for immunizing a patient, comprising administering multiple conjugates of meningococcal capsular saccharides, wherein each conjugate comprises a diphtheria toxoid (or derivative thereof) carrier protein, and the capsular saccharide, and wherein the patient has been pre-immunized with a diphtheria toxoid (or derivative thereof).