Increased international travelling, an increased number of patients with immunosuppression caused by HIV infection, and renewed interest in known but little studied microorganisms, resulted in a more frequent finding of certain medically important parasites. Three emerging protozoal infection, Cyclospora cayetanensis, Dientamoeba fragilis and Microspora (Enterocytozoon bieneusi and Encephalitizoon) are causative agents of diarrhoea. Encephalitozoon infections are also associated with hepatitis, hepatoconjunctivitis and nephritis. C. cayetanensis infection was diagnosed in 28 patients in the years 1992-1995 in the Academic Medical Centre in Amsterdam, half of these patients returning from a visit to Indonesia. D. fragilis has a prevalence in the Netherlands of 8% among patients with diarrhoea lasting longer than one week referred for parasitological investigation. The prevalence of E. bieneusi in HIV positive patients with diarrhoea was 8-10% in the Academic Medical Centre in the last five years. Infection with Encephalitozoon appears to be endemic in the Netherlands.