Rift Valley fever (RVF) is an acute, zoonotic viral disease, caused by a Phlebovirus belonging to the Bunyaviridae family. RVF virus (RVFV) historically has been responsible for large explosive outbreaks of severe human and animal disease throughout Africa and recently in the Arabian Peninsula. In animals, it mainly affects domestic ruminants such as sheep, goats and cattle. RVFV outbreaks among livestock are economically devastating and often characterized by large sweeping abortion storms and significant mortality in adult livestock. This study was conducted to investigate RVF infection in Kigoma region. Regional wide serosurvey and conventional gel based single tube RT-PCR were conducted in Kigoma region on non- vaccinated small ruminants (sheep and goats). The study included 411 animals (32 sheep and 379 goats) sampled in 3 districts namely; Kigoma rural, Kasulu and Kibondo. Sera of animals were tested for the detection of immunoglobulins G (IgG) against RVFV using commercial enzyme-linked immunosorbent assays (ELISA) kit. Past infections were detected in 22 of 411 animals (5.4% at 95% CI 3.5 % to 8.1%) from all three districts. Kigoma rural recorded higher seroprevalence of 12.0% (CI 7.3% to 18.3%; P<0.0001) followed by Kibondo (2.3% [0.5% to 6.5%]; P>0.05) and Kasulu districts (0.8% [0.0% to 4.2%]; P>0.05). The prevalence was 12.5% and 4.7% for sheep and goats respectively. RT-PCR results indicated that only 8 samples were found positive (n=63) including 22 positive samples for IgG ELISA, where none was RT-PCR positive. This study has confirmed, for the first time, the presence of RVFV in Kigoma region, 4 years after the 2007 epizootic in Tanzania, and suggests further that the virus activity exists during the interepizootic period (IEP) even in regions with no history of RVF. In-depth studies should be conducted to clarify the complex epidemiology of RVF in the country.Southern African Centre for Infectious Disease Surveillance (SACIDS)