Syphilis, in all stages, is almost eradicated in Norway. Since 1993, only six to 17 patients have been registered per year. However, syphilis rates are increasing in some of Norway's neighbouring countries, e.g. Russia and the Baltic countries. Physicians must be aware of the disease. We report three patients admitted to an emergency psychiatric ward in Oslo, diagnosed with neurosyphilis during 1994-97. Doctor's delay in diagnosing was respectively seven and fifteen months for two of these patients. The diagnosis is difficult, for many reasons: The disease is rare; it can mimic several other diseases; incidental partial treatment with antibiotics given for other disorders may complicate the clinical picture; it may be difficult to obtain a reliable history; and new clinical pictures ("formes frustes") may occur. The traditional syphilis screening is not recommendable, but physicians' awareness and a low threshold for requiring syphilis serology tests is important in order to get an early diagnosis of one of the few curable psychiatric disorders.