BACKGROUND Namibia, located on the southwestern coast of southern Africa, is characterized by vast deserts, limited fresh water, and low population density. Mortality estimates among children <5 of age are 63 deaths per 1000 live-births, with diarrheal diseases contributing to 3% of these deaths. Data on the burden of rotavirus disease and circulating serotypes in Namibia are currently not available. METHODS From May 1998 through December 1999, 815 stool specimens were collected from children <5 years of age who attended the Windhoek State Hospital, Windhoek, Namibia, for diarrhea. Specimens were screened for the presence of rotavirus antigens. Rotavirus-positive specimens were further analyzed to determine electropherotype, subgroup (SG) specificity, and G and P genotypes. RESULTS Rotavirus was detected in 113 (13.8%) of 815 specimens, with the majority of infections occurring in children <18 months of age. Strains bearing 1 long electropherotype, SGII, and G1P[8] or G1P[6] specificity predominated during the 20-month study period. In addition to the typical winter rotavirus season, a peak in rotavirus infection was also observed during the summer. CONCLUSIONS Serotypes G1P[8], G1P[6], G1P[4], and G2P[4] were found throughout the study period, predominantly in children <18 months of age. The observed summer rotavirus peak coincided with increased rainfall in Namibia and an increase in the diversity of detected serotypes. During the October to December 1999 peak, 2 G9P[6] strains and 1 G8P[4] strain were identified. Expanded and updated information on prevalence of rotavirus infection, circulating serotypes, and burden of disease will be required to enable local government to make decisions on the implementation of rotavirus vaccination in Namibia.