This paper examines the effects of ascribed status on individual achievement. It contains two parts: (1) the status attainment research in the United States, and (2) the specification of status attainment model for the study of social mobility in Taiwan. In the first part, the various status attainment models for the study of social mobility in the U.S. are examined. It concludes that family background variables in various models explain approximately 40% of the variance of occupational status and less than 20% of the variance of income differences in the United States. Therefore, the American society is a relatively open society in the sense that the individual's achievements are not strongly influenced by his social origins. In the second part, the author specifies a status attainment model and the measurements of its variables for the study of social mobility in Taiwan. The author suggests using father's education, occupational status and income as social origin variables, and son's education, occupational status and income as achievement variables. Using path analysis, the effects of social origins on individual's achievements can thereby be calculated.