The study reported in this paper examines clinical reasoning styles with a focus on laboratory utilization. A stratified sample of 80 physicians participated in the solution of a simulated patient management problem. The analysis focuses on variation in the portfolio of laboratory tests ordered as a function of practice setting (e.g., physicians in practice versus physicians in training). The study also examines the response of physicians to the imposition of constraints on ordering, as well as behavior, when unlimited ordering capacity is provided. Overall, the data profiles emerging from the analysis indicate the variety inherent in physician decision-making strategies, and point to the necessity of employing a cautious and flexible approach toward any general scheme of constraints upon medical diagnostic procedures.