To study the epidemiology of small round-structured viruses (SRSV) in the Netherlands, all outbreaks of gastroenteritis that were reported to the Research Laboratory for Infectious Diseases, Department of Virology, National Institute of Public Health and the Environment (RIVM) in 1994 and 1995 were examined using electron microscopy (EM), single-round reverse transcription-polymerase chain reaction (RT-PCR), and sequencing. To enable this, a generic SRSV-specific primer pair was developed that could detect 85% of a panel of antigenically diverse SRSV. By EM, SRSV could be detected in 86% and by RT-PCR in 91% of the reported gastroenteritis outbreaks. Partial sequence analysis of the polymerase region of these viruses revealed that two different clusters of viruses were responsible for the majority of the outbreaks. This strongly suggests epidemic spread of SRSV in the Netherlands.