The purpose of this study was to identify the influential factors engaged in the instructional development practitioner \'s decision-making process to investigate the dynamics of reflecting front- end analysis results on corporate instructional development process. The questions of this research were proposed as follows ; 1) Are the front- end analysis results applied to corporate instructional development strictly as they are? 2) What are the factors influenced on the modification of front- end analysis results, if the front- end analysis results are not applied strictly to the ISD process? To answer these questions, a qualitative case study, with its emphasis on description rather than prescription, was chosen to cast light on the dynamic interplay of critical factors on the ID practitioner \'s decision-making process. The data collection techniques used were followings : (1) content analysis to clarify the differences between the front- end analysis results and the final version of the training program, (2) interview techniques to find out the reasons and factors for the differences, (3) post data analysis to categorize data and to delineate the critical factors and their pattern. Findings were summarized as follows : 1. Front- end analysis results are not applied to corporate instructional development strictly. 2. Factors on corporate instructional development practitioner \'s decision- making are followings : (1) characteristics of the practitioner (the project manager), (2) client needs and style, (3) implementation environment, (4) political dynamics around project manager, (5) front- end analysis errors, (6) resource availability, (7) cultural context. 3. The most critical factor of these were characteristics of practitioner (project manager) and practitioner \'s individual style, practitioner \'s intuition / insight, practitioner \'s academic or work experience, practitioner \'s philosophy on instruction. 4. Other factors had also subordinate factors ; \"Client needs and style\" included client needs, client support and style, client \'s perception of the corporate instructional development. \"Implementation environment\" included instructor \'s role and level, learner \'s level and motivation, schedule convenience, limit of facilities. \"Political dynamics around project manager\" included the political dynamics with stakeholders and project team members. Factors were discussed on comparison with previous studies and were found to influence on the corporate instructional development practitioner \'s decision-making process with concurrent, holistic dynamics. Findings indicated that the application of ISD model in corporate instructional development were neither step-by- step nor sequential process, but were influenced by dynamics of various factors. It suggested that the impact of these factors should be considered when utilizing ISD models in corporate instructional development. And front- end analysis should be performed in consideration of the dynamics of these factors.