This paper reviews and discusses the results of five cross-cultural studies in Colombia, Costa Rica, El Salvador, Spain, and USA, using 2 (college students vs. their parents) × 2 (males vs. females) MANOVA match group designs with the Attitudes and Beliefs Inventory subscales as dependent variables, two multicultural studies investigating the relationship between some demographic variables (Pan American Health Organization's Index of Violence, and Acculturation) and people's Irrationality, and two multidisciplinary studies on the relationship between some medical conditions (skin diseases, and severity of symptoms during menopause) and Irrational Beliefs.