G12 rotavirus has not been detected anywhere in the world since the first detection of a human strain, L26 (G12, P1B[4]), in the Philippines in 1990. In this study, we isolated a human rotavirus (strain T152) with a VP7 of G12 specificity from the stool of an 11-month-old diarrheic patient in Thailand. The strain T152 exhibited a long RNA pattern and subgroup I specificity. In the comparison of the nucleotide and amino acid sequences of the VP7 gene of strain T152 with those of rotaviruses with different G type specificities, strain T152 showed the highest identity, 90.9 and 93.9%, respectively, to G12 prototype strain L26. In contrast, the VP4 gene of strain T152 showed the highest identity with P[9] specificity of human strains K8 and AU-1 and feline strains Cat2 and FRV-1, with homologies of 89.3 to 90.6% at the nucleotide level and 93.9 to 95.6% at the amino acid level. Thus, strain T152 was found to be a natural reassortant strain with G12 and P[9] specificities.