Three randomised, blinded and placebo-controlled laboratory studies were conducted to evaluate the efficacy of emodepside plus toltrazuril suspension (Procox(®) suspension for dogs) against Isospora canis and Isospora ohioensis-complex. Unweaned puppies were experimentally infected with sporulated oocysts of I. canis and/or I. ohioensis-complex. In each study, one group was treated during prepatency (2 or 4 days post infection) while dogs in the second group were treated individually after the onset of oocyst excretion of the respective coccidia species. The dogs were treated with the minimum therapeutic dose of 0.45 mg emodepside and 9 mg toltrazuril per kg body weight. Daily faecal oocyst counts from both groups were compared to placebotreated control groups to determine efficacy.Dogs treated during prepatent I. canis or I. ohioensis-complex infection showed significantly lower oocyst counts for up to 12 days compared to the control group. Oocyst counts were reduced by 90.2 - 100 % while the control groups continued to exhibit an adequate infection, except for one study where efficacy against prepatent I. canis infection faded 13 days after treatment. Following treatment of patent I. canis or I. ohioensis-complex infections, significantly lowered oocyst counts were observed for up to 9 days compared to the control group. Faecal oocyst counts were reduced by 91.5 - 100 %. In all three studies the number of days with diarrhoea was significantly lower when dogs were treated during prepatent Isospora spp. infection compared to the control groups. No adverse drug reactions were observed during the studies. In conclusion, the studies demonstrated that emodepside plus toltrazuril suspension is an efficient coccidiocide for dogs.