Ribeiro M. G., Belotta A. F., Fernandes M. C., Guena R., Nardi Junior G., Lara G. H. B., Giuffrida R. & Zamprogna T.O. 2011. [Fine needle aspiration in diagnosis of lymphadenitis in sheep.] Citologia aspirativa no diagnostico da linfadenite em ovinos. Pesquisa Veterinaria Brasileira 31(10):839-843. Departamento de Higiene Veterinaria e Sa de Publica, Faculdade de Medicina Veterinaria e Zootecnia, Universidade Estadual Paulista, Cx. Postal 560, Botucatu, SP 18618-970, Brazil. E-mail: mgribeiro@fmvz.unesp.br The fine needle aspiration in diagnosis of lymphadenitis in sheep, and occurrence of microorganisms in the lymph nodes, with emphasis to identification of Corynebacterium pseudotuberculosis were investigated. One hundred sheep with lymphadenitis and 100 lymph nodes without lesions collected from sheep in slaughterhouses were evaluated. C. pseudotuberculosis (73.0%), Arcanobacterium pyogenes (6.0%), Streptococcus spp. beta hemolytic (5.0) and Escherichia coli (4.0%) were the more frequent causal agents in sheep with lymphadenitis. Streptococcus spp. (21.0%) and Staphylococcus spp. (7.0%) were the more common microorganisms identified in lymph nodes without lesions sampled in slaughterhouse. Fine needle aspiration enable identify 79 (79.0%) microorganisms with "corynebacteria" aspect in sheep with lymphadenitis. From these, 73 (73.0%) were identified as C. pseudotuberculosis. None strain of C. pseudotuberculosis was isolated from lymph nodes of animals without lesions. The results showed the high frequency of C. pseudotuberculosis in sheep with lymphadenitis, and possibility the use of fine needle aspiration in initial diagnosis of lymphadenitis in sheep.