Dengue fever is a viral disease transmitted by Aedes aegypti. It has been recently incorporated to the agenda of priorities in many countries in the Americas. The emergence of dengue hemorrhagic fever cases is becoming a public health threat and requires the implementation of intensive surveillance and control strategies. The epidemiological panorama of dengue in Mexico provides the opportunity to analyze a regional health problem and the risk factors involved in the genesis of hemorrhagic cases under a situation that has not reached epidemic proportions yet.