The purpose of this study was to examine the relationship between teachers' teaching effectiveness and school effectiveness in comprehensive high schools in Taiwan, Republic of China. The establishment of comprehensive high schools signals a new type of secondary education. In order to improve the quality of education in comprehensive high schools, it is necessary to examine their school effectiveness. Furthermore, Reynolds (1998) and Wu (2002) both indicated that teachers play an important role in classroom activities. To ensure educational quality and improve school effectiveness, it is necessary to investigate the relationship between teachers' teaching effectiveness and school effectiveness of these schools. This study collected data from 832 teachers in comprehensive high schools in Taiwan during the spring semester of 2004, using a questionnaire that was composed of background information, the Teachers' Teaching Effectiveness Scale and the School Effectiveness Inventory. Pilot tests of these two instruments were conducted to yield the formal research questionnaire. Finally, the data collected was analyzed by statistical methods including frequency, percentage, mean, standard deviation, reliability test, t-test, one-way ANOVA, one-way Multivariate Analysis of Variance, Scheffe method, Pearson product-moment correlation, canonical correlation, and stepwise multiple regression model. The major findings and conclusions were: (1) The levels of teaching effectiveness measures of comprehensive high school teachers were moderately high, with "good teacher student relationship" being the highest, and "teaching self efficacy" being the lowest. (2) The levels of school effectiveness measures of comprehensive high schools were moderately high, with "principal leadership" being the highest, and "curriculum implementation" being the lowest. (3) Gender, age, teaching experience, teaching program, school size, type of school, and school educational level, position, school area, and school background were not related to teachers' teaching effectiveness. (4) Gender, age, teaching experience, teaching program, school area, type of school, school background, and school history were significant to school effectiveness, while educational level and position were not related to school effectiveness. (5) The higher the teachers' teaching effectiveness, the higher the school effectiveness. (6) Canonical analysis results showed that "systematical presentation of instructional materials" was positively related to "teaching and evaluation" and "student achievements", and "teaching self-efficacy" was positively related to "student achievements" and "teachers' job satisfaction". (7) Gender, type of school, "teaching self efficacy", "systematical presentation of instructional materials" and "good classroom climate" were the five best predictors for school effectiveness. Based on the results of this study, some implications are drawn. (Contains 2 tables and 1 figure.)