Microsystems used for chemical analyses and biological assays are termed BioMEMS or labs-on-a-chip.These systems often require some of the traditional electromechanical capabilities of MEMS,and in addition require the manipulation of fluids in either continuous flow or droplet form.The distinction between continuous flow and droplets defines two broad categories of BioMEMS.Different applications call for one or the other of these approaches,but in either case,software for design and simulation can make a significant contribution to design optimization and reduction in time to market.A computer aided design and analysis approach is presented in which system-level analysis is favored over detailed analysis,although it is shown that this is not always possible,nor preferred.Examples of the use of design and analysis software in BioMEMS development are presented including:electrostatic actuation,a lab-on-a-chip for separation,on-chip optics,a digital fluidic processor,electro-spray ionization,and a two-stage chemical reaction.