The resistance of Balamuthia mandrillaris to physical, chemical and radiological conditions was tested. Following treatments, viability was determined by culturing amoebae on human brain microvascular endothelial cells for up to 12 days. B. mandrillaris cysts were resistant to repeated freeze–thawing (five times), temperatures of up to 70 6C, 0.5% SDS, 25 p.p.m. chlorine, 10 mg pentamidine isethionate ml”1 and 200 mJ UV irradiation cm”2.