During the period May 1987-January 1989, faecal samples from 417 paediatric inpatients admitted to the main paediatric hospital in Rome were screened by direct electron microscopy and rotavirus enzyme-linked immunosorbent assay. Rotaviruses were detected in 18.2% of cases and adenoviruses in 7%, whereas astroviruses were found in 1% of cases. Different percentages of rotavirus excretors were revealed by enzyme-linked immunosorbent assay and electron microscopy. This discrepancy seems to be due to false positive results introduced by enzyme-linked immunosorbent assay. Analysis of electron microscopy-positive samples by rotaviral RNA polyacrylamide gel electrophoresis showed different electropherotypes of rotavirus among which a single, largely predominant long electropherotype (55.4%) was revealed. Short electropherotype subgroup I rotaviruses were demonstrated in about 10.7% of samples.