The numbers of tests, imaging and diagnostic procedures ordered by doctors in primary care and hospital settings alike are rising. According to established guidelines, many of these tests may be unnecessary. Various non-clinical factors often underlie test ordering, and multiple prevalent problems associated with tests and their interpretation are often under-appreciated. These include the significant potential for cascades of further testing and patient harm. Multifaceted strategies may improve test-ordering behaviour. Brief reconsideration of several points by the clinician before ordering the test is advisable.