The aim of the present study was to evaluate the efficacy of thiabendazole on the treatment of Otodectes cynotis infestations in dogs. Ten naturally infested beagle dogs were used. The mites were diagnosed through otoscopy. Dogs were examined three days before treatment (day -3) and on the treatment day (day 0). They were randomly divided into two groups, five animals for the control group and five for the treated. During seven days, was applied in both ears of the treated dogs 1ml of the thiabendazole 5% solution, which correspond to 50mg of the product. All animals were reexamined through otoscopy on days +1, +3, +7, +10, +17, +24 and +31. The dogs on the control group showed mites in both ears during the whole period of observation. On the treated group the efficacy varied from 20% on the left ear to 80% on the right ear, on the first day after treatment. On days +3, +7, +10, +17, +24 and +31 the medium efficacy was 100% on both ears. The thiabendazole was efficient on the elimination of O. cynotis in dogs when used on the dose of 50mg per ear during seven following days.