To describe the circulation dynamics of human rotavirus genotypes and to understand the epidemiological changes of rotavirus infection in Turkey, one of the countries where the highest mortality rates are seen due to rotavirus in Europe. Stool samples of children under 5 years of age which gave positive results for rotavirus antigen were stored at -20 degrees C and then genotyped using multiplex reverse transcription polymerase-chain reaction. Of the 494 stool samples, 137 (28.1%) were positive for rotavirus antigen and 100 (73%) samples which could be genotyped successfully were included in the study. 42 (42%) samples were from inpatients, and 58 (58%) were from outpatients. The median age of the children was 16 months (5 days-59 months). G9 and P were the most frequent G and P genotypes, and were detected in 30 (30%) and 55 patients (55%), respectively. In 90 samples for which both G and P genotypes could be determined, 34 different combinations were found. G9P was the most frequent genotype detected in 19 patients (19%), followed by G1P and G4P each in 7 (7%) patients. The incidence of mixed infection was found to be 26%. Novel strains like P2A and P and unusual reassortant strains were detected. Distribution of rotavirus genotypes exhibited distinctive changes in this study. When the everchanging epidemiology of rotaviruses is taken into account, ongoing surveillance studies are important before the inclusion of rotavirus vaccines in national immunization program of Turkey.