Dengue fever is a viral disease, transmitted to man via mosquito bites. It is endemic in tropical regions (10 million infected annually) and is characterized by high fever, headache, myalgia, lethargy, vomiting, rash and neutropenia. The upward trend in the number of young Israelis visiting tropical countries increases the number of those potentially exposed to this disease. We present 4 Israelis who returned with dengue fever from Thailand.