Objectives To report the consequences of the computer system breakdown for three New York hospitals involved with the terrorist attack of September 11, the immediate measures performed to maintain function, and the following recovery and planning processes. Methodology Analysis of the experiences from the course of the event both with regard to the computer systems, the urgent salvage procedures, the impact on the functions in the hospitals, the existance/function of reserve systems, and the impact on planning for the future. Results The analysis showed an extensive dependence on computer technology for all functions in the hospitals and to a great extent abscense of prepared reserve or backup procedures. A dramatic cross-campus effort saved and restored the computer operations of the three involved hospitals, using Mount Sinai's resources as a backup. The experiences resulted in a plan to minimize or if possible eliminate these risks for dysfunction of the medical care system in similar events in the fut...