ABSTRACT. Carrasco L.P.S., Oliveira R.L.S., Moreira C.M.R., Santos C.R.G.R., Corgozinho K.B. & Souza H.J.M. [Cryptosporidium diagnosis by qPCR in cats at Rio de Janeiro state, Brazil.] Diagnóstico de Cryptosporidium spp. pela técnica de qPCR em gatos no estado do Rio de Janeiro, Brasil. Revista Brasileira de Medicina Veterinária, 38(Supl.):22-26, 2016. Programa de Pós-Graduação em MedicinaVeteriná- ria, Instituto de Veterinária, Universidade Federal Rural do Rio de Janeiro, BR-465, Km 7, Seropédica, RJ 23890-000, Brasil. E-mail: firstname.lastname@example.org Cryptosporidium spp. is recognized as an important etiologic agent of diarrhea in many countries. The aim of this study was to detect the presence of DNA of the parasite Cryptosporidium spp. in feces of cats with history of chronic diarrhea attended in the Feline Medicine Sector of the Veterinary Hospital of the Federal Rural University of Rio de Janeiro, by the polymerase chain reaction technique in real time (RT-PCR). In this study, 100 animals were admitted, of any breed or sex and from 8 weeks of age. As inclusion criteria, patients had to have diarrhea history for more than three weeks, with little success of clinical response to previously established therapies. From the samples obtained by collecting via washing the animal colon and spontaneous defecation, methods of direct examination of the feces, centrifugal flotation technique and real-time PCR were carried out. Of all cats selected for this study, 10% showed infection by Cryptosporidium spp. Most positive animals were aged over one year (70%) and only 30% had up to one year old. Cats were 50% purebred and 50% were domestic short hair cats. The clinical signs presented by these cats at the time of consultation were diarrhea (60%) and prolapsed rectum (40%). Four animals had co-infections with other enteropathogens (40%), such as Giardia, Toxocara sp. or Tritrichomonas fetus alone or combined. We concluded that infection by Cryptosporidium spp. is an important differential diagnosis in cats with chronic diarrhea, in cats of all ages and regardless of whether purebred or not, may have the infection and co-infection with other enteric pathogens needs to be investigated in all cases.