Abstract: One pathogenic free-living amoeba, strain W042302 (Fig. 1.), was first isolated from the cooling water of a power plant in Shanghai, in April, 1986. It could result in the deaths of mice, and recovered from the brain tissue of the dead mice. This pathogenic free living amoeba could be induced into trophozoite with two flagellae (Fig. 2.). Protein patterns obtained by PAGE showed twelve bands stained by Coomassie brilliant blue R250. The isoenzyme patterns of both acid phosphatase and alkaline phosphatase of the amoebic extract exhibit only a single band, while iactate dehydrogenase is devoid of noticeable activity. From the results obtained in the present study, it is inferred that strain W042302 may be belong to Naegleria australiensis.