We determined the frequency of certain disagreeable physical characteristics (presence of vomitus, dentures, blood and/or alcohol on the breath) of a cardiac arrest patient and the effect these characteristics have on a bystander's willingness to perform CPR. Data were collected prospectively on 121 nontraumatic cardiac arrest patients, of whom 35 received bystander-initiated CPR involving a total of 42 bystanders. Seventy-one (59%) patients had one or more disagreeable characteristics identified. Forty (33%) patients vomited; 39 (33%) wore dentures; five (4%) had alcohol on their breath; and nine (7%) had visible blood. Of the 42 bystanders involved, 14 were exposed to one or more of the disagreeable characteristics. No bystander interviewed indicated hesitancy in performing CPR when encountering disagreeable characteristics. Seven bystanders stated they felt inadequately prepared to handle patients who vomited. Because of the high incidence of disagreeable characteristics, notably vomitus, in patients suffering a cardiac arrest, specific training in handling such characteristics seems justified.