Background: Various quantitative systems have been proposed to examine aphasic oral narratives in English. A clinical tool for assessing discourse produced by Cantonese-speaking persons with aphasia (PWA), namely Main Concept Analysis (MCA), was developed recently for quantifying the presence, accuracy and completeness of a narrative. Similar tools for Mandarin speakers are currently absent. Aims: The first aim is to develop and establish the validity of the Taiwanese Mandarin Main Concept Analysis (TM-MCA) for the Mandarin-speaking population in Taiwan, given the paucity of related investigations. Another aim is to establish the influence of age and education level on Taiwanese Mandarin speakers' oral narrative abilities. The third purpose is to examine how well the TM-MCA could distinguish between native speakers with and without aphasia in Taiwan. The final aim is to examine the reliability and validity of the TM-MCA. Methods & Procedures: Eight speech-language pathologists (SLPs) and eight neurologically intact participants were involved to establish the TM-MCA main concepts. Another 36 neurologically intact participants and 10 PWA participated to validate the TM-MCA by contrasting their performance. Outcomes & Results: Both age and educational level affected the oral discourse performance among the neurologically intact adults. Significant differences on the TM-MCA measures were noted between the control group and the group with aphasia. Moreover, the degree of aphasia significantly affected the oral discourse of PWA. Conclusions & Implications: The TM-MCA is a culturally appropriate quantitative system for the Taiwanese Mandarin population. It can be used to supplement standardized aphasia tests to help SLPs make more informative decisions not only on clinical diagnosis but also on treatment planning.