ABSTRACT. Silva S.R., Lourenço E.C., Tassinari W.S. & Famadas K.M. [Descriptive study of the historical series of tick occurrence in dogs assisted in two animal health units in the western zone of the city of Rio de Janeiro.] Estudo descritivo da série histórica de ocorrência de carrapatos em cães assistidos em duas unidades privadas de saúde animal na zona oeste da cidade do Rio de Janeiro. Revista Brasileira de Medicina Veterinária, 38(supl. 3):249-259, 2016. Programa de Pós-Graduação em Ciências Veterinárias, Universidade Federal Rural do Rio de Janeiro, BR465, Km 7, Seropédica, RJ 23890-000, Brasil. E-mail: firstname.lastname@example.org. Despite ticks relevance for public health, few studies have been carried out aiming at the epidemiology of these parasites in urban environment. There is no study of time series data for tick occurrence, which would be very useful for animal health professionals regarding the prophylaxis and control of these parasites. The aim of this work was to describe the historical series of tick occurrence in dogs assisted in two private animal health units in urban environment, from January 2000 to December 2014. The Noch test was used to verify differences in prevalence between the years, and the chi-square test, to evaluate the prevalence of tick occurrence between the months and between the years. The correlation between prevalence of tick occurrence and temperature was also performed. One thousand and five hundred veterinary medical records were systematically selected. The records of parasitism between the years were not uniform. In 2003, 2004 and 2009 were observed the highest prevalence, 43.00%, 31.00% and 31.00%, respectively in relation to the other years. In February (26,00%) and September (11,80%) were observed the highest and lowest values, respectively, with no differences. No seasonal patterns or temporal trend of the prevalence of tick occurrence in dogs were observed in the study area. There is no evidence that temperature influences the increase in the prevalence of tick occurrence in dogs in the urban environment. We suggest the inclusion in the animal care records of the specific diagnosis and stage of the tick, as well as the number of ticks observed in the examination of the animal so that more detailed epidemiological studies involving tick / dog can be performed. The inclusion in the animal care records of the specific diagnosis and stage of the tick, as well as the number of ticks observed in the examination of the animal was considered very important so that more detailed epidemiological studies involving tick/dog can be performed.