Faecal samples from 137 patients that had been shown to contain adenoviruses by electron microscopy were identified in a series of enzyme immunoassays (EIA) using a single monoclonal antibody (Mab) to adenovirus 40 and four different Mabs to adenovirus 41. Adenoviruses were partially characterised by restriction enzyme analysis (REA) of DNA extracts using SmaI. Samples were also run in a commercial EIA (Adenovirus IDEIA; Dako, Ltd.) which detects group antigen. The majority (84%) of adenoviruses were subgenus F: adenovirus type 41, 87 (64%) and adenovirus type 40, 28 (20.4%). Subgenus A viruses were identified in ten, (7%) patients, eight were type 31, and two type 12. The adeno IDEIA test was sensitive and specific, detecting 127 of 131 positives and giving no false-positive results with other enteric viruses. Use of monoclonal-based EIAs showed significant differences depending on which adeno 41 Mab was used, although the restriction patterns obtained using SmaI appeared to be identical for 66 of 69 samples that produced recognisable bands. The Mab that performed best, M 4.3.1, was raised against strains obtained from children in England and detected 83 of 84 (99%) of the adenovirus 41 samples tested. In contrast Mab JH/41 raised against the prototype strain of adenovirus 41 (Tak) detected only 69 of 87 (79%).