A team of physicians, pharmacists, and informatics professionals developed a CDSS added to a commercial electronic medical record system to provide prescribers with patient-specific maximum dosing recommendations based on renal function. We tracked the time spent by team members and used US national averages of relevant hourly wages to estimate costs. 924.5 hours and $48,668.57 in estimated costs were needed to develop 94 alerts for 62 drugs. The most time intensive phase of the project was preparing the contents of the CDSS (482.25 hours, $27,455.61). Physicians were the team members with the highest time commitment (414.25 hours, $25,902.04). Estimates under alternative scenarios found lower total cost estimates with the existence of a valid renal dosing database ($34,200.71) or an existing decision support add-on for renal dosing ($23,6944.51). Development of a CDSS for a commercial computerized prescriber order entry system requires extensive commitment of personnel, particularly among clinical staff.