An integrated enabling technological infrastructure is mission critical to health systems. The integration of disparate legacy systems carries great risk, and failures or dislocations are not uncommon. Best practices for system integration at all systems of the systems life cycle can reduce these risks, as can attention to human factors within a change management framework. Systems integration remains a transitional solution at best. To reduce medical errors and improve the health care system, future systems must provide the interoperability that vendors of new applications architectures promise.