This paper describes a combined evaluation approach for an information system on intensive care units. Staff self assessment of time needed for documentation activities during admission, daily treatment and discharge/transfer has been compared to a workflow analysis which demonstrated that the system eliminated process steps mainly in daily documentation activities. Interestingly, nursing staff reported major time savings rather during discharge/transfer than in daily documentation, whereas physicians noticed no time savings at all. We conclude that combining workflow analysis with either self assessment of time needed or alternatively appropriate time measurements or both increases insight into organizational changes and their implications after system implementation.