This study has focused on genetical patterns of rotavirus positives on diarrhea patients in Incheon. Fecal specimens collected from January 2002 to December 2004 from patients with diarrhea in seven localities in Incheon were screened for group A rotavirus by RT-PCR. To survey the prevalence of group A rotavirus infection and distribution of P (VP4) and G (VP7) genotypes of rotaviruses in Incheon, we performed the nested RT-PCR using rotavirus ELISA positive samples. Among a total of 4,865 samples investigated, 1,100 samples (22.6%) were positive. The predominant genotypes of 293 RT-PCR positive samples were confirmed as G4P[6] (101 samples, 34.5%) followed by G2P[4] (73 samples, 24.9%), G1P[8] (38 samples, 13.0%), G3P[8] (28 samples, 9.6%), G3P[10] (14 samples, 4.8%), G4P[8] (6 samples, 2.0%) and G9P[8] (6 samples, 2.0%). Mixed types and untypable types were 3.8% and 5.1%, respectively. The most prevalent types in 2002, 2003 and 2004 were G4P[6] (71 samples, 40.3%), G4P[6] (22 samples, 40.7%) and G2P[4] (15 samples, 22.2%) respectively. This is the first nationwide genoepidemiological study for determining the prevailing of genotypes of rotaviruses in Incheon. The genetic analysis for investigating sequence variations among group A rotavirus strains in this study would provide the useful information to establish the preventing strategy of human rotaviruses and of developing vaccines which will be used in Korea.