This study reports on exploratory research that investigated biology teachers' perceptions of their online information seeking practices and how these practices influenced their instructional planning activities. Quantitative and qualitative analyses of the results of an online survey and ten in-depth interviews measuring use of specific online tools (i.e., search engines, specific Web sites, digital libraries, online periodical databases, and electronic discussion lists) were conducted. Key findings show that teachers are using a greater number and wider range of current and multimodal resources than pre-Internet and perceive this as an advantage in creating authentic, inquiry-based learning experiences. However, underuse of educational online resources specifically designed to support teaching and learning activities (e.g., digital libraries, online periodical databases, and electronic discussion lists) was evidenced. Four themes reflecting the consequences of teachers' information seeking practices emerged from the data analysis: Currency of Information; Sparking of Ideas and Gaining Personal Knowledge; Resource Management and the Role of Time; and Webs of Sharing. Each theme encompassed both the purposeful and the indirect actions by teachers to access knowledge and resources to refine and improve their instructional planning. Study findings have implications for informing the collaborative relationship between school library media specialists and teachers. (Contains 5 tables and 6 figures.)