Human pythiosis is caused by Pythium insidiosum, often found in patients in tropical and subtropical area especially in developing countries. The infections arise though coming in contact with zoospore of P. insidiosum. The disease may be manifested as a cutaneous/subcutaneous, ophthalmic, vascular or disseminated type. The identification of P. insidiosum isolated in human is time consuming, and requires skilled personel. It can be carried out by culturing and inducing the formation of zoospores, immunological technique, and molecular technique. At present, treatment has not been successful. However, improved sensitivity and specificity of diagnosis by healthcare professionals will surely result in a more effective treatment.