E-Learning systems that produce personalized course offerings for the learner are often expensive, both from a time and financial perspective, to develop and maintain. Learning content personalized to a learners' cognitive preferences has been shown to produce more effective learning, however many approaches to realizing this form of personalization involve considerable re-authoring of existing learning material. To reduce the implementation overhead on the content author and course designer it is imperative to facilitate the maximum reuse of learning resources. This paper investigates a standards-based approach to delivering personalized learning content to learners using World Wide Web technologies. Detailed is an implementation of a personalized e-Learning service, called the OPen Adaptive Learning Environment (OPAL), which is based on delivering content personalized to the learner's cognitive and presentation learning preferences using aggregation models based on ADL SCORM (ADL) (Advanced Distributed Learning Sharable Content Object Reference Model). (Contains 15 references.) (Author)