Strongyloidiasis is an intestinal parasitic disease caused by Strongyloides stercoralis. Basically, detecting larvae of S. stercoralis in feces makes definitive diagnosis. The ordinary agar plate culture method developed at our department is much simpler to handle and much more sensitive than the conventional filter paper culture method. It is considered to be the most useful method in the diagnosis of strongyloidiasis and in evaluation of the eradicating effect. Among chemotherapeutic agents, thiabendazole representing the benzimidazole compounds is most effective. However, it has a problem in safety, since its adverse effects and liver dysfunction occur with a high incidence, and it can be severe. Regarding the effects of mebendazole, albendazole and ivermectin, a study was conducted which included many patients. A high incidence of liver dysfunction was observed with mebendazole, and eradicating effect was not sufficient with albendazole. Ivermectin is different from benzimidazole compounds in a pharmacokinetic profile. However, ivermectin showed a strong anthelmintic effect with the least toxicity. We therefore consider ivermectin is the most useful drug for the treatment of strongyloidiasis.