Of a total of 508 stool specimens from children with acute diarrhoea, mostly under the age of 5 years, collected in nine cities in the western and southeastern regions of Turkey between May 2000 and October 2002, 119 (23·4%) were found positive for rotaviruses (RV) by ELISA. Positive samples were characterized by electropherotyping and G and P genotyping. A subset of G and P types were confirmed by nucleic acid sequencing. The most prevalent types found in this collection included G4P[8], accounting for 27/64 (42·2%) of the fully characterized strains. G1P[8], G2P[4] and G3P[8] were found in 17 (26·6%), 2 (3·1%) and one (1·5%) samples respectively. Less common strains such as G9P[8] were found in two (3·2%) samples and G2P[8], G1P[6], G2P[6] and G4P[6], possible reassortant viruses, were found in five (7·8%), 2 (3·1%), one (1·5%) and four (6·3%) samples respectively. Mixed infections were found in six (7·3%) samples and were associated with combinations of G1+G2, G1+G4, G1+G9 and G4+G9 strains. This is the first molecular epidemiology study of its kind to be carried out in Turkey and suggests a significant diversity of co-circulating rotavirus strains.