To evaluate the risk of colonisation with N meningitidis among university classroom contacts of a student with invasive meningococcal disease.Throat cultures were obtained from classmates and faculty exposed to a university student with meningococcal disease. Exposures to the index case were quantified using a questionnaire.None of the 41 students and staff from whom cultures were obtained showed evidence of colonisation with N meningitidis. The contacts had spent an average of 13.5 h in class with the index case during the 2 days prior to the onset of her illness.The risk of colonisation with N meningitidis among casual university classroom contacts appears to be low. This study lends support to decisions to withhold chemoprophylaxis in most instances of such contact.