Hepatitis delta virus (HDV) is a subviral satellite of human hepatitis B virus (HBV). HDV was discovered in patients chronically infected with HBV who had a more severe form of disease. Subsequent studies have attempted to understand the cytopathic effects due to HDV, and this article reviews the progress along with newer studies that suggest that HDV genome replication per se causes no more than a moderate inhibition of cellular growth rate. This inhibition nevertheless provides a selective pressure for reduced levels of HDV genome replication. Such a reduction is apparently achieved by a host cell activity that edits the HDV RNA genome.