One hundred and twenty adult and 80 human fetal skulls were examined to find the relationship (if any) between the presence of wormian bones in the lambdoidal suture and artificial deformation of the skull. Wormian bones occur in deformed and undeformed skulls with no significant differences. Wormian bones detected in fetal skulls preclude cultural deformation as an important factor in the formation of these bones. It is hypothesized that a genetic predisposition (genes allowing formation of secondary ossification centers) is present and that wormian bones are under direct genetic control regardless of the presence or absence of detectable cultural deformation.