Background: Outcomes and costs of inpatient versus outpatient pediatric cardiac catheterization have not been extensively evaluated. Methods: For a cost-consequence analysis, we reviewed the medical records and cost data in a Swiss pediatric hospital. We compared outcomes and costs of observed inpatient management versus hypothetical planned same-day discharge for patients meeting the outpatient catheterization criterions for an American pediatric hospital. Results: Among 346 catheterization admissions occurring from January, 1998 through December, 1999, 179 met the American criterions for outpatient catheterization. Complications observed, and/or nursing interventions begun within 5 hours of catheterization, might have required overnight observation in 41 of the 179 admissions (22.9%). The remaining 138 patients were stable at five hours, and presumably could have been discharged the day of the procedure. Routine pre-discharge imaging detected significant complications following three interventional procedures. Postulated costs from the perspective of the provider, counting hospital and physician expenditure were calculated for the Swiss franc in 2000 at a rate of 1.69 francs for each American dollar, averaged 10,946 francs per inpatient, versus 9790 francs for outpatient treatment (p < 0.001 by paired t-test). Estimated revenue deficits, calculated as costs minus reimbursement, averaged 8565 francs per inpatient versus 1756 francs per patient treated as an outpatient. Conclusions: Half the patients being catheterized in the Swiss hospital met the external criterions for attempted outpatient catheterization. Most might have been safely discharged on the same day, with modest savings in costs, and reduced deficits in terms of revenue. Routine pre-discharge imaging may be more important than overnight observation. Outpatient catheterization merits prospective evaluation in Switzerland.