In this study, microcalorimetric measurements were carried out on PK-15 cell line persistently infected by cholera swine fever virus (CSFV) and BHK-21 cell line infected by foot and mouth disease virus (FMDV). The aim of this investigation was to investigate the difference of energy metabolism between the different kinds of virus infections-persistent infection and cytocidal infection. The thermogenesis curves determined by using a LKB 2277 Bioactivity Monitor were significantly different. From these thermogenic curves, the maximum heat production rate P-m and total heat output Q are obtained. The results show that energy metabolism is different between persistent infection and cytocidal infection. (C) 2003 Elsevier Science B.V. All rights reserved.