Viral food-borne illnesses have become very common in humans worldwide. Three viruses—noroviruses, rotavirus, and hepatitis A virus (HAV)—are implicated frequently in food-borne illness and have been ranked among the top 10 causes of food-borne disease over the past 10 years. The most common food vehicles for the transmission of enteric viruses to humans are shellfish, fruits, and vegetables. Foods may be contaminated by water tainted with untreated sewage or by contact with infected human food handlers. Virus concentrations in foods are usually low, as they are not able to multiply in situ . Therefore, the ability to detect traces of viruses in foods is essential in the development of tools for the investigation and possible prevention of viral disease outbreaks. Molecular approaches based on the amplification of viral RNA have been proposed for the specific and ultrasensitive detection of enteric viruses in foods. Nucleic acid sequence-based amplification (NASBA) is one of these molecular techniques showing great promise in viral detection. In this chapter, we describe two applications using NASBA techniques for the detection of hepatitis A virus and rotavirus.