Pesq. Vet. Bras. 34(3):211-216, março 2014 211 RESUMO. No Brasil, dados relacionados com a ocorrência de neoplasias em ruminantes e equinos são escassos. Objetivou-se com este trabalho determinar a frequência de neoplasias diagnosticadas em bovinos, caprinos, ovinos e equí-deos no Laboratório de Patologia Animal da Universidade Federal de Campina Grande, Patos, Paraíba, durante o perí-odo de 1983 a 2010 e analisar os fatores de risco, mediante o teste de qui-quadrado, considerando como variáveis, espécie, raça, sexo e idade. Durante o período foram registrados 177 (5,6%) tumores de um total de 3.153 diagnósticos provenientes de biópsias e necropsias. Houve diferenças significantes (p<0,001) na frequência de tumores entre as diferentes espécies sendo mais acometidos os equinos (10,6%), seguidos pelos bovinos (6,8%), caprinos (3,3%) e ovinos In Brazil, data related to occurrence of tumors in livestock are scarce. The objective of this study was to determine the frequency of tumors diagnosed in equidae, cattle, sheep and goats in the Pathology Laboratory of the Federal University of Campina Grande, Patos, state of Paraíba, from 1983 to 2010, and to analyze the risk factors by the chi square test, considering variables such as species, breed, age and sex. During the period, 177 (5.6%) out of 3153 specimens from biopsies or necropsies were diagnosed as tumors. There were significant differences (p<0.001) in the frequency of tumors among different species; horses (10.6%) were more affected than cattle (6.8%), and cattle were more affected than goats (3.3%) and sheep (2.1%). Squamous cell carcinoma was most frequent tumor in cattle (58.3% of the tumors), sheep (80%) and goats (46.1%), and sarcoid (45.3%) was the most frequent in horses. Regarding the location, neoplasms were more common in the skin of horses (62.5%) and sheep (60%), in the eyes and periocular skin in cattle (36.1%), and un the female reproductive system (perineal region and vulva) of goats (34.6%). Regarding the sex of the animals, only cattle had significant prevalence (p<0.001). Regarding age only goats showed significant prevalence (p=0.015). There was no significant prevalence in any animal species in relation to race. We concluded that squamous cell carcinomas in ruminants and equine sarcoid are the most common tumors in livestock in the semiarid Brazilian Northeast, and the equidae were the most affected among the species studied.