The purpose of this study is to analyze how readers with varying prior knowledge navigate in hypertext learning environments. A standardized networked-structure hyper textual environment was developed by the first author and it was used as the learning material. Readers' navigation paths and time duration on each page were recorded in log files. In addition, readers' eye movements were also recorded during their navigation. Data analyzes showed that readers' navigation patterns were differed across their prior knowledge levels. Low prior knowledge (LPK) readers felt more disoriented than high level prior knowledge (HPK) readers. Moreover, LPK readers were observed to navigate at the surface, rather than deep level. Navigational patterns and eye movement data also supported these findings.