Micro-pumps utilizing no-moving-parts (NMP) valves, driven by a piezoelectric element bonded to a flexible membrane have been developed by a number of research groups (Olsson et al, 1995a; Forster et al, 1995; Gerlach and Wurmus, 1995). Recently, pump heads of over 7 m of H2O have been achieved (Olsson et al, 1996). However, no systematic methods have been reported that predict pump performance and guide the design of optimally performing pumps. We have developed a linearized dynamic system model that provides a detailed understanding of the relationship between a realistic set of system parameters and pump performance. These parameters include flow characteristics of the NMP valves, characteristics of the working fluid, pump geometry, and materials used in fabrication. Utilization of the model as a design tool, resulted in a dramatic improvement from previous “flexible” pump designs with maximum heads of approximately 0.24 m of H2O to a “stiff” design with a maximum head of 4.75 m of H2O, a twenty-fold increase in performance. Corresponding flow rates increased from 85 to 750 μl/min, a nine-fold increase.