The aim of this study was to evaluate the pathogenicity of Isospora species in dogs.

For this purpose, four dogs that had complaints such as bloody diarrhea, weakness, fatigue were examined in that Eimeria oocysts. After the examination of stool, detected oocyst were sporulated in 2.5% potassiun dichromate at 22 ºC and species identification were made.

As a result, Isospora canis and Isospora ohioensis species were identified at all of dogs. Although one of infected dog were dead before treatment, others were treated with sulphamezhatine and these three dogs recovered.

In conclusion, we emphasized that Isospora species can cause clinical infection especially in transported, younger and bad nursed dogs.