Available evidence suggests that persons with serious forms of mental illness are 4–10 times more likely to commit homicide as compared to non-affected members of the general population. The relationship between homicide and psychotic illness has now been subject to longitudinal investigation in six different populations across eight studies covering time periods over the last six decades. With the exception of one study, these investigations demonstrate that homicide associated with psychotic illness appears relatively stable through time and, in most populations, is not related to factors that contribute to the rise and fall of total population homicide (TPH) rates. This suggests that illness and treatment factors are of most importance if we are to reduce the prevalence of this tragic illness complication.