This guidance provides a method and rationale for designing monitoring networks to determine compliance with newly enacted PM 2.5 and PM 10 national ambient air quality standards. It defines concepts and terms of network design, presents a methodology for defining planning areas and community monitoring zones, identifies data resources and the uses of those resources for network design, and provides some practical examples of applying the guidance. Existing metropolitan statistical areas are first examined to determine where the majority of the people live in each state. These are then broken down into smaller populated entities which may include country, zip code, census tract, or census block boundaries. Combinations of these population entities are combined to define metropolitan planning areas. These may be further sub-divided into community monitoring zones, based on examination of existing PM measurements, source locations, terrain, and meteorology. Finally, PM 2.5 monitors are located at specific sites that represent neighborhood or urban scales to determine compliance with the annual standard and at maximum, population oriented locations for comparison with the 24-hour standard.