The aim of this study was to evaluate the WCST, a task linked to the frontal (prefrontal) cortex, in normal twins to detect an inherited component of frontal lobe function. The WCST scores of 15 monozygotic (MZ) twin pairs, 9 dizygotic (DZ) twin pairs, and 15 unrelated control pairs were used to compute genetic estimates. No significant differences were detected between MZ, DZ and control groups intrapair correlation coefficients. No significant herita-bility estimates different by zero were computed. The frontal lobe function measured by WCST performance in normal twins does not seem to have a high degree of genetic component, and larger samples of twins are required to detect low genetic effects. The possible implications of such results about the genetic predisposition of frontal deficit in schizophrenia have been discussed.