Two patients were hospitalized on account of high pyrexia and ill-defined symptoms. Both were receiving Nomifesin as the only form of medication. The pyrexia disappeared on withdrawal of the drug and no other explanation could be found for the symptoms. Provocation with Nomifensin was attempted in both of the patients after they had become free from symptoms, and fever was immediately reproduced. 5 other cases with similar symptoms have been reported to the Danish Committee on Side-effects of Drugs.