Two experiments were conducted to see if blood drive attendance could be increased by altering the content of reminder calls. In Experiment 1 college students received either a standard reminder (the place, time, and necessity of eating beforehand) or a commitment-enhancing reminder in which they agreed to be “counted on”. Those in the latter condition were significantly more likely (p <.007) to attend a blood drive. Experiment 2 demonstrated that an alternate wording for the commitment-enhancing message was possible; that a verbal response was necessary to ensure the commitment; and that a message enhancing altruism was not as effective. The studies suggest that asking for an additional commitment during a reminder call can appreciably increase blood drive participation rates.