Concomitant Medications are medications used by patients in a clinical trial, other than the investigational drug. These data are routinely collected in clinical trials. The data are usually collected in a longitudinal manner, for the duration of patients' participation in the trial. The routine summaries of this data are incidence-type, describing whether or not a medication was ever administered during the study. The longitudinal aspect of the data is essentially ignored. The aim of this article is to suggest exploratory methods for graphically displaying the longitudinal features of the data using a well-established estimator called the ‘mean cumulative function’. This estimator permits summary and a graphical display of the data, and preparation of some statistical tests to compare between groups. This estimator may also incorporate information on censoring of patient data. Copyright © 2009 John Wiley & Sons, Ltd.