Methodological aspects of a study are reviewed to illustrate the utility of the case study approach in researching the effectiveness of a motivational intervention in an instructor-facilitated learning context. In the study, learners were prompted via motivational messages into modifying their disposition to engage in learning tasks. The setting was an instructional design course for training personnel connected with a ministry in Mozambique. Subjects were 22 regular employees of the ministry and seven special students with limited time to participate; the sample included 19 males and 10 females. A naturalistic mode of inquiry was identified as the most appropriate one for the inquiry and a case study approach, from an embedded multiple-case perspective, was chosen. Basic research questions included: (1) the validity of the motivational messages; (2) how and why the messages worked; and (3) the messages' optimal function and its continuation over time. Of the 10 propositions formed about the messages and the learners, instructor, and environment, nine were found to hold true when tested in the original study and a second study 3 years later. It is concluded that motivational messages should be considered an integrating part of a complex motivational system. The case study approach was found well-suited to the research concerns. (SLD)