White spot is an important parasitic disease causing serious economical loses in cultured freshwater fish and the causative agent, Ichthyophthirius multifiliis is an ectoparasitic ciliate.In the present study, in order to determine effective therapeutants on different stages of I. multifiliis (theront, tomont and cyst) therapeutants acriflavin neutral, metranidazole, methylene blue, potassium permanganate, sodyum klorur, chloramine-T, chloramphenicol, oxytetracycline, tribressen, furazolidone were investigated in vitro. The effects of therapeutants on survival rates of the parasite individuals in different stages were evaluated with the aid of a scala of 0 (100% effective); + (75% effective); ++ (30-40% effective); +++ (non-effective). While Sodium chloride (3%, 2%, 1%), metranidazole (1‰), methylene blue (1‰) and potassium permanganate (1‰) were effective on all stages of the parasite but oxytetracycline (1‰), furazolidone (1‰) and tribrissen (1‰) had no effect on all stages of the parasite. On the other hand, it was determined that acriflavine neutral, chloramin-T and chloramphenical were effective against theront and tomont stages of the parasite but these therapeutants were ineffective against cysts.