One hundred and fifteen faecal samples from children with gastroenteritis have been examined by solid-phase immune electron microscopy (SPIEM), standard direct electron microscopy and enzyme-linked immunosorbent assay (ELISA). Diluted high-titered anti-(human) rotavirus serum, produced in rabbit by immunization with purified pooled rotaviruses from gastroenteritis patients, was used as antiserum in the immunological tests. The presence of rotavirus was demonstrated in 41 (36%) of the 115 samples by both SPIEM and ELISA. No false positive reactions were seen. By direct electron microscopy rotavirus was detected in 35 (30%) of the specimens. In addition, other gastroenteritis viruses like adeno-, astro- and calicivirus were visualized by this non-specific test in eight samples. The applicability of these three methods in routine diagnostic work is discussed.