Dermatophytosis is a superficial mycosis caused mainly by Microsporum canis and is very common in Persian cats. The goals of this study were: to evaluate the clinical and mycological cure in the animals treated with terbinafine in pulse therapy compared with continuous therapy; the accumulation of terbinafine in cats hair and the time that it is maintained in therapeutic concentrations after its suspension; correlation between the clinical cure with the amount of the drug in the hair and, to compare the side effects in pulse therapy in relation to continuous therapy. In this study were included 27 Persian cats, 17 healthy carriers of M. canis and 10 cats with dermatophytosis. Group I was composed of 13 females treated with pulse therapy, during the first seven days at the dose of 20 mg/kg, daily, followed by a period of suspension of the medication for 21 days, subsequently, it was done a new cycle of terbinafine, therapy was performed for additional seven days at the dose of 40 mg/kg daily, repeating a period of suspension for another 21 days. Group II was composed of 14 males, that received continuous therapy, during 56 days. On the first month they received the oral dose of 20 mg/kg daily and 40 mg/kg daily for the next 28 days. The animals were submitted to two mycological cultures collected by the carpet square method with 15 days of interval, before and after the therapy. Cats' hair was also collected by manual avulsion for the quantification of terbinafine by high performance liquid chromatography (HPLC) in the days zero, seven, 28, 35 and 56. Every 15 days, blood samples were obtained for hepatic function evaluation. There were clinical and mycological cure in 100% of treated animals; the concentrations of terbinafine in cats´ hair were maintained above therapeutic concentrations in pulse therapy at the dose of 20 mg/kg, and also at 40 mg/kg daily oral administration, but there was a higher accumulation of the drug when it was used in the higher doses and continuous therapy. However emesis was observed in the first week of therapy, and also higher hepatic enzymes serum activities. There were no alterations in the values of ALT and FA in the pulse therapy group. Terbinafine had good efficacy and was safe for the treatment of healthy carriers of M. canis and also for animals with dermatophytosis.