The changes in the concentrations of infectious coxsackie B3 virus (detected by cell culture), and the viral genome (detected by RT semi-nested PCR), when the virus is kept at 25°C in sterile phosphate buffered saline (PBS) and in PBS plus clay was monitored. The viral genome survived for twice as long as the infectious virus. The survival of the genome was greatly prolonged by adding 200 mg l−1 Na–montmorillonite to the PBS, while the survival of the infectious virus was only slightly increased. The T90 of the viral genome was at least 3.5 times longer that the T90 of the infectious virus. Thus, the rate of decay of the viral genome is different from that of the infectious virus.