Technical Abstract: Health care is in the midst of a consumer-oriented technology explosion. Individuals of all ages and backgrounds have discovered eHealth. But the challenges of implementing and evaluating eHealth are just beginning to surface, and, as technology changes, new challenges emerge. Evaluation is critical to the future of eHealth. This article addresses four dimensions of eHealth evaluation: (1) design and methodology issues; (2) challenges related to the technology itself; (3) environmental issues that are not specific to eHealth but pose special problems for eHealth researchers; and (4) logistic or administrative concerns of the evaluation methodology selected. We suggest that these four dimensions must be integrated to provide a holistic framework for designing and implementing eHealth research projects, as well as for understanding the totality of the eHealth intervention. The framework must be flexible enough to adapt to a variety of end users, regardless of whether the end user is a healthcare organization, a for-profit business, a community organization, or an individual. The framework is depicted as a puzzle with four interlocking pieces.