The major purpose of this paper is to measure segmented labor markets (also known as dual labor markets) based on the Taiwanese official two-digit occupational groups. The mean statistics on 14 criterion variables for each two-digit occupation, pooled and calculated from three kinds of data conducted by the Directorate-General of Budget, Accounting and Statistics (DGBAS), were used to classify namely upper primary, lower primary, and secondary labor markets. The results of classifications generated from four different approaches, such as Z-value approach, Factor Analysis approach, Cluster Analysis approach, and Kaufman approach, were compared and discussed. Finally, several construct validity tests indicate that the Z-value approach is the most parsimonious choice for defining occupational segmented labor markets. In addition, the histogram of the index of occupational quality constructed from the Z-value approach has shown a multi-modality pattern, which was found in the analyses using the unit of either occupational or individual level. The multi-modality pattern provides a demarcation line to define occupational segments, and such a pattern has not been shown or even used to define occupational segments in previous studies. The shares of individuals in the upper primary occupations are around 19% of the total labor force between 1981 and 1992. The increasing shares of individuals located in the lower primary occupations (16.63%, 18.90%, and 23.69% in 1981, 1985, and 1992 respectively) coincide with the rapid development of service industries in Taiwan during the period. In addition, the shares of secondary occupations decreased across time, such as 63.65%, 62.80%, and 54.92% in 1981, 1985, and 1992 respectively. The shrinking of jobs in the secondary occupations might be related to de-industrialization in Taiwan during the period.