There has been much attention devoted to microfluidic systems in recent years, and it has become clear that electrokinetics is one of the favored methods to drive systems with flow channel dimensions in the tens of microns and flow rates in the nanoliter per second range. At these small dimensions, sample and reagent consumption is very small, and analysis speeds are greatly improved. At Caliper, we have demonstrated applications including DNA separations, enzyme assays, and cell biology. Others in this field have shown other examples of applications, such as immunoassays on a chip. The trend in electrokinetically driven microfluidic circuits is toward more complexity and functionality, which has mostly been achieved through the use of parallelism. It is tempting to regard this as an extension of Moore's law, which predicts a constant rate of increase of the functionality of an electronic integrated circuit. This raises the issue of the scaling laws governing microfluidic circuits, and what the limits are the scaling will run into. This presentation will discuss the scaling laws for simple circuits such as a four-port device for injection and separation, followed by an analysis of the design issues involved in parallel devices.