A 28 item version of the Wilson-Patterson Attitude Inventory was administered to 345 participants (twins, spouses, friends, and others) in the Minnesota Study of Twins Reared Apart. An overall conservatism measure demonstrated impressive construct validity. It had strong convergent validity, demonstrated by correlations of 0.72 and 0.58 with the Altemeyer Right Wing Authoritarianism scale and the Multidimensional Personality Questionnaire (MPQ) Traditionalism Scale, respectively. It also had strong discriminant validity, being largely uncorrelated with the other 10 MPQ Scales and WAIS Full Scale IQ. Heritabilities were calculated from fitting models to the variance-covariance matricies based on 54 pairs of monozygotic (MZ) and 46 pairs of dizygotic (DZ) twins reared apart. Conservatism demonstrated significant and sizeable genetic influence (h 2 = 0.56), replicating the results reported in the Virginia 30,000 study of ordinary twins and family members and those of a large Australian twin study.