To many educators, Web-based training (WBT) is the constructivist ideal--learners can construct meaning through self-directed inquiry, guided activity, and group collaboration on the information highway, the digital library, cyberspace, or the global village. Although research on the effectiveness of WBT as a vehicle for constructivist learning is scanty, findings from other areas can be applied. For example, WBT provides full, rich information from innumerable sources, can accommodate differences among learners, allows learning activities that foster construction of meaning, and helps instructors make the change from giver of knowledge to guide, facilitator, and coach. Although the technology of WBT allows, enables, and promotes constructivist learning, WBT does not always deliver in practice. Reasons include: that some learners need new technology skills, some instructors have difficulty incorporating WBT into their teaching, some instructors find it difficult to function as a guide, and the amount of information available can be overwhelming or be out of date. Considering advantages and disadvantages, one could conclude that although enormous amounts of information can be available on the Web, it is not always accessible or usable. In addition, although WBT has the capability needed for allowing learners to construct meaningful learning, it is not always used, and it may not always be appropriate. Implications for policy and practice show that instructional design, not merely technology for its own sake, should drive the use of WBT and that learners and instructors need appropriate training to take advantage of this approach. (Contains 18 references.) (KC)