Coordination is central in CSCW systems design, where it is often considered as a process of bringing artifacts and activities together and making them part of a larger system. In this paper, we argue that existing conceptualizations of coordination in CSCW can be successfully extended with the notion of coordination by avoidance. We introduce this notion to describe particular coordination mechanisms whereby actors avoid routines or routes of actions when it conflicts with those of other actors. In a study of pre-diagnostic work, we found that actors coordinate by avoidance when they realize alternative routes of action or that a routine has to be set to a halt to ensure that practices stay coordinated. Routines in diagnostic work are for instance the rescheduling of patients and requesting of relevant patient records that are mundane practices, however, necessary when responsibility is shared or shifts between various actors collaborating to diagnose a patient. Thus, the contributio...