本研究目的在探討國小高年級學童課外閱讀的自我決定動機，並了解其與個人背景變項（性別、 年級）、閱讀行為、閱讀理解表現之間的關係。研究對象為高屏地區925 位國小高年級學童。工 具包括閱讀自我決定動機量表、閱讀行為調查表、國小高年級閱讀理解測驗。所得資料以集群 分析、百分比同質性檢定及單因子多變量變異數分析進行統計分析。主要結果包括：1. 國小高 年級學童在課外閱讀自我決定動機上可分為六個不同群組。2. 不同性別的國小高年級學童在課 外閱讀自我決定動機群組上有差異。3. 不同年級的國小高年級學童在課外閱讀自我決定動機群 組上有差異。4. 不同課外閱讀自我決定動機群組的學童在閱讀行為上有差異。5. 不同課外閱讀 自我決定動機群組的學童在閱讀理解表現上有差異。研究結果支持了自我決定在國小高年級學 童的課外閱讀動機上所扮演的關鍵角色。最後，本研究根據研究結果，提出對於閱讀實務以及 未來研究的建議。

The purpose of this study was to investigate self-determined motivation for extracurricular reading among fifth and sixth graders as well as to explore its relationships with background variables (gender, grade), reading behavior, and reading comprehension. The participants were 925 fifth and sixth graders in Kaohsiung City and Pingtung County. They took the Self-Determined Reading Motivation Scale, the Reading Activity Inventory, and the Reading Comprehension Test. Statistical methods included cluster analysis, test of homogeneity of proportions, and one-way multivariate analysis of variance. We found that: (a) in estimating the fifth and sixth grade students' self-determined motivation profiles in extracurricular reading, a six-cluster solution emerged; (b) gender differences were found among the six clusters of self-determined motivation; (c) grade differences were found among the six clusters of self-determined motivation; (d) differences on reading behaviors were found among the six clusters of self-determined motivation; and (e) differences on reading comprehension were found among the six clusters of self-determined motivation. The results supported the crucial role of self-determination in students’ motivation for extracurricular reading. Finally, based upon the results, we provided suggestions for reading practices and future studies.