In Argentina the presence of rotavirus was investigated in a chicken flock experiencing periodic episodes of diarrhoea during the winter of 1986. All the samples analysed were negative by the enzyme-linked immunosorbent assay (ELISA). However, when samples were observed by electron microscopy, particles which were indistinguishable from standard rotaviruses were detected in some samples. Ten of the 36 samples were positive after polyacrylamide gel electrophoresis (PAGE) analysis, all of them showing the same electropherotype. Based on these results these viruses were classified as rotavirus-like or atypical rotaviruses.