Field and commensal rodents and shrews were live-trapped from selected areas in each of the six zones of the Republic, namely North-eastern, Eastern, Central-western, South-western, Southern and Seaports. The captured animals, small ruminants, humans and small carnivores were serologically tested for specific plague antibodies, using the Passive haemagglutination (PHA) and Passive haemagglutination Inhibition (PHAI) techniques. Taxonomic studies and population densities of rodents and their ectoparasasites were carried out. A total of 5638 animals were captured and 79.9% of them were tested for plague. Of those tested, 2.4% contained agglutinating plague antibodies at serum dilutions of 1:20 and above. The positive rodents were found in Lushoto, Mbulu, Chunya and Monduli districts, as well as at Tanga seaport. These include R. rattus, M. natalensis, A. niloticus and Otomys spp. A total of 7480 human, 293 carnivorous and 425 small ruminant sera were also tested for plague. Seven (2.4%) of the carnivores were positive at serum titres of 1:20-1:80. All the small ruminants were negative. Likewise, 1.4% of the tested human sera contained specific plague antibodies at titres ranging from 1:20-1:60. Out of 6480 fleas collected from the captured small mammals, 5476 were identified. Of these, 34.5%, 20.4%, and 17.8% were X. brasiliensis, D. lypusus and X. cheopis respectively. It was generally concluded that plague was still endemic in several parts of the country, that some foci were active, and that there was a potential risk of accidental introduction and/or transfer of the disease into or out of the country. Establishment and maintenance of surveillance services and facilitating research and control programmes of the disease were recommended.