 Background Rotavirus gastroenteritis is an essential cause of morbidity and mortality among under five years children in the developing countries.  Aim: Determination of its incidence and serotypes.  Methods: It is a prospective cross-sectional study conducted in a tertiary hospital in Sana' as part of regional surveillance for rotavirus. Children <5 years with acute diarrhea were eligible for enrollment. The stool samples were collected and tested according to standard WHO guideline. Rotavirus was tested using enzyme linked immunoassay and the serotypes by PCR at the Regional Rotavirus Reference Laboratory, Cairo, Egypt. The data was processed and analyzed using Epi info program (version, 2008).  Results: The incidence rate of Rotavirus was 24.4%. G12 constitutes 45.5%, G2 constitutes 19.5%, G1, and G9 14% each and G3 2.6% of the samples. The genotyping of P gene showed that P[8] constitutes 78% of the samples, P[4] 17%, P[6] 4%, and the un-typable (UT) only 1% of the samples. The rate of G-P combinations showed that G12P[8] in thirty-four samples; G2P[4] in thirteen samples, G1P[8] in eleven samples; G9P[8] in ten samples ; G[UT] P[8] in three samples; G2P[6] and G3P[8] in two samples each; and G9P[6] in one sample.  Conclusion: The incidence rate of Rotavirus in Sana'a didn't change much despite the introduction of the vaccine. This could be attributed to the emergence of new serotypes such G12 and G9 that were not covered by the Rotarix vaccine. There will be a strong need to develop a new vaccine that cover these new emerging serotypes.

Keywords : Rotavirus, Children, Serotypes, Sana'a.