Sir: Mir & Taylor (Psychiatric Bulletin, December 1999, 23, 742-747) in their review of serotonin syndrome reminded us of the diagnostic criteria (Sternbach's criteria) for the diagnosis of this syndrome at a time when we had recently changed the drug therapy of a patient from trazodone to paroxetine. In this patient we saw the emergence of five symptoms listed in Sternbach's criteria (agitation, myoclonus, shivering, tremor and incoordination). We have two points to make: we noted that the most severe symptoms in this patient were nausea and vomiting. Although, it is accepted that nausea and vomiting may occur as part of the serotonin syndrome (Reference Lane and BaldwinLane & Baldwin, 1997) they are not diagnostic criteria. Gastrointestinal symptoms are well-recognised effects of increased serotoninergic activity and it is surprising that there is little emphasis on them in the literature relating to this subject. Where serotonin syndrome is a result of changing drug therapy the possibility of a discontinuation syndrome should be considered as an alternative diagnosis because of the overlap in symptomatology between the two syndromes.