In this article, we review the criteria used to establish a causal ass
ociation. A literature search strategy will be outlined. We present a
clinical scenario that was formulated to examine the evidence for nons
teroidal anti-inflammatory drugs as a possible cause of gastrointestin
al ulceration and bleeding. Several of the studies identified in the l
iterature search were critically appraised and the criteria needed to
confirm a causal link were then applied. These guidelines may be emplo
yed to not only demonstrate the aetiology of a disease but have wider
applicability in terms of determining whether a medication may be caus
ing certain adverse events.