SummarySome important biological and physico‐chemical characteristics of porcine circovirus are reported. These include a study on the host distribution in nature, levels of colostrum‐derived antibodies in piglets from sero‐positive sows and the susceptibility of a range of cell cultures to infection with this virus. The results of haemagglutination studies, resistance to pH 3, chloroform and heat are also reported as are comparative buoyant densities and sedimentation coefficients of porcine circovirus and chicken anaemia