Since structural dimensions of knowledge and learner contribute to preferred message structure, an understanding of structural relationships can aid in the more effective design of instructional messages. Five studies were conducted to explore these relationships. Knowledge structure was defined as the iconic representation of the body of knowledge in question, learner structure as those stable response tendencies predictive of learner behavior, and message structure as the temporal order in which elements within iconic structures are presented to learners. Graduate education students were asked to respond to a range of iconic knowledge structures. Judgments, problem-solving, and verbal learning were explored. The distribution of response frequencies suggested that learning can be facilitated or retarded according to the structure of the message and that different types of learning may call for different types of message structure. Findings on the role of individual differences were inconclusive. Preferred temporal order of message elements in an iconic knowledge structure was found to be dependent on the kind of structure in question rather than on the content of the message. (Chi-square analysis, p<.001). (LS)