The present work was conducted in the equipe population of the jockey club of Pelotas, RS, with the objective of determining the presence and titer of serum antibody for the type 1, 2 and 3 reovirus and the influenza virus A/equi-1 and Alequi-2. All the serum samples were examined by the hemaglutination inhibition test (micromethod).The serotype 3 reovirus showed the highest prevalence (P < 0.01). It has been found that a higher prevalence of multiple reactions to three serotypes in animals older than 5 year of age. Eightyfour percent (84%) of the variation of the prevalence (r2 + 0.84) can be explained by the increase of age (Y = 9.43 + 5.42X, P < 0.05), but no correlation was observed between sex, serotypes and prevalence of positives. Low prevalences were observed for influenza virus serotypes Alequi-1 (0.49%) and Alequi-2 (0.98%). In an outbreak during this period, two viral strains were isolated possibly a rhinovirus. These results suggest that reoviruses are present in the horses studied, however, their relationship with respiratory disease was not confrmed. These results showed also that this population of horses is completely susceptible to the influenza viruses.&nbsp;Se estudi&oacute; la presencia de anticuerpos s&eacute;ricos frente a los reovirus 1, 2 y 3 y de los virus influenza A/equi-1 y A/equi-2 en los equinos del Jockey Club de Pelotas. Se realiz&oacute; la prueba de inhibici&oacute;n de la hemoaglut&iexcl;naci&oacute;n (microm&eacute;todo). El serotipo 3 del reovirus present&oacute; mayor prevalencia (P &lt; 0,01). Se detect&oacute; mayor prevalencia de animales con m&aacute;s de 5 a&ntilde;os de edad reaccionando con los tres serotipos del reovirus simult&aacute;neamente, y las variaciones de las prevalencias pueden explicarse por el incremen&shy;to de la edad (Y = 9,43 + 5,42 x, R2 = 0,84% P &lt; 0,05). No se observ&oacute; relaci&oacute;n entre sexo y preva&shy;lencia para ning&uacute;n serotipo de reovirus. Las preva&shy;lencias para influenza fueron de 0,49% para A/ equi-1 y 0,98% para A/equi-2. Adem&aacute;s, se aislaron dos cepas de un virus que caus&oacute; un brote de enfer&shy;medad respiratoria en la poblaci&oacute;n estudiada; sin embargo, no relacionado con los reovirus y virus influenza, probablemente un rinovirus. Los resulta&shy;dos obtenidos sugieren que los reovirus est&aacute;n pre&shy;sentes en los equinos estudiados, pero no se ha demostrado su relaci&oacute;n con enfermedad cl&iacute;nica. Se comprueba tambi&eacute;n que la poblaci&oacute;n estudiada no presenta protecci&oacute;n frente a la influenza equina. &nbsp;