This chapter presents the practical biological, engineering, monetary, educational, and service considerations intended to aid the potential user in evaluating how the instrumented system meets the goals of speed, accuracy, and reasonable cost. It discusses the engineer's special problems in designing an instrument system for analysis of potentially hazardous living organisms. Controlling of the size of the inoculum is an important factor in instrumented microbiological analyses. Some of the instrumented procedures for susceptibility testing direct that the inoculum be prepared by picking several "similar" colonies. Most rapid instrumented procedures for microbiological analyses of body fluids are performed on actively growing cultures in broth medium. Among the practical considerations in designing or purchasing an automated or partially automated instrumented system for microbiological analysis is the potential future uses of the instrumented system, with or without additions or modifications. Design of instruments for microbiological analysis of potentially infectious specimens poses special problems for the engineer.