The driving force for undertaking any process retrofit is to increase the overall profitability of that process. The opportunities for increasing profitability are available in a wide variety of forms. For example, cheaper, alternative raw materials, which do not affect the yields and cycle time, may be identified. A new conversion or recovery technology to produce the same compound may be developed. The average throughput of the slowest stage, the bottleneck, may be increased by adding parallel equipment or by fine-tuning operating parameters of that stage. Of course, any process change may incur capital expenses and/or increase operating costs which must be more than offset by the increase in the overall throughput of the process. The management at Eli Lilly has made a commitment to base the process retrofit decisions on as much quantitative information as possible. In addition, an increased emphasis will be placed on taking into consideration the overall process in evaluating the impact of change rather than studying a section of the process in isolation. Due to the highly regulated nature of the pharmaceutical business, the cost and risk of implementing a process change are enhanced. Making changes to a pharmaceutical process entails obtaining regulatory compliance approval. The extent of effort required in obtaining these approvals depends on the types of proposed changes. Some changes require only proper reporting, while others require proper validation and authorization by the FDA. Often, unless the indicated change has a proposed significant incremental improvement, it would be rejected. Simulation has provided additional support to justify both major and minor process improvements. This paper describes the steps taken in evaluating the impact of changing the technology of a key operation in one section of Eli Lilly's biosynthetic bulk drug processing facility in Indianapolis, IN. The study was performed using the BATCHES simulator. First, the description of the underlying process is given followed by the details of the simulation model. At the end, a summary of various simulation runs and the ranges of parameters studied is provided.