In this study, the design and plasma generation principle of a microwave induced plasma sterilization technique is described. Generation of low temperature argon plasma was investigated for different microwave power densities. Inactivation effects of the plasma were studied on bio-indicators carrying Escherichia coli as a function of microwave power density and particularly for different locations of the bio-indicator holder. The results showed that argon plasma having a temperature below 60 degreesC are generated having less than 4.21 w/cm(3) of microwave power density at an ambient temperature of 34 degreesC. Survival of E.coli was significantly reduced when the microwave power density of the plasma treatments increased. While, high inactivation was observed at the center, it was less effective at the two opposite edges of the bio-indicator holder. (C) 2002 Elsevier Science Ltd. All rights reserved.