Personality disorders have a long history in the literature but a short scientific history. The point prevalence of personality disorders is 10%, but the lifetime prevalence is probably 30–40%. Genetic factors contribute to around 40–50% of the variation in the development of personality disorders. The effect of shared environment is very small or non-existent. Some researchers have tried to promote gene-environment interaction. However, in reality, the studies investigated gene-situation interaction, as the “environment” may in reality be partly of a genetic nature. Thus, we are dealing with an unknown part of gene-gene interaction. Gene-experience (not gene-environment) correlations are the rule in human life. Personality disorders co-occur (are comorbid) with symptom disorders (Axis I) and correlate with common personality dimensions. Possibly, the concept of personality disorder could merge with dysfunctional personality types. But it is likely that the concept will survive on its own.