Between September 2004 and December 2005 a prospective study was conducted to understand the epidemiology of rotavirus infection among children with diarrhea attending two hospitals in Ankara, Turkey. Rotavirus was detected in 39.7% of the 322 stool samples and affected mainly children in the age group of 6-23 months. More than 70% and 39% of these cases occurred in children <2 and <1 year of age, respectively. In the temperate climate of Ankara rotavirus infection was prevalent throughout the year. Serotype G1P[8] was dominant followed by G9P[8]. In 38 samples a total of 5 electropherotypes were detected. All G9P[8] were of long electropherotype except one of short electropherotype. A proportion of G1 and G9 strains were in combination with P[6], P[4] or P nontypable. Mixed serotypes were responsible for 2.4% of the infections. A phylogenetic tree constructed with the deduced amino acid sequences of the VP7 gene showed that 16 Turkish G9 strains clustered with rotaviruses of lineage III. One G9 strain formed a new lineage, lineage IV with the Sri Lankan G9 rotaviruses. In the phylogenetic tree of the VP8* gene, the Turkish G9P[6] rotaviruses clustered with human strains of lineage Ia. Increased diversity of the G/P type combination and the presence of infection throughout the year in Turkey was a situation similar to developing countries. The occurrence of rotavirus infection at later age and low level of mixed infections in Turkey represented the situation of developed countries. This study suggests that diverse G9 rotaviruses are emerging in Turkey.