The development of molecular biology techniques has modified research procedures for certain viruses, particularly hepatitis A virus (HAV) and enteroviruses. Accordingly, we designed cDNA and RNA genomic probes to detect viruses in shellfish in the environment. Better sensitivity was noted with RNA than cDNA probes: only 17/83 shellfish samples were positive with HAV and enterovirus DNA probes, where as 42/83 were positive with HAV and enterovirus RNA probes.