The papers describes epidemiologic designs and methods in studies of health effects of air pollution, whose implications, however, can be extended to the detection of health effects of other environmental exposures. Recent advances in measurement technology for the assessment of both exposure and health responses and rapid developments in the field of biological markers of both exposure and health response offer the opportunity to rectify some past weaknesses or gaps in our ability to draw firm conclusions from environmental epidemiologic studies. Different design strategies for epidemiologic studies of acute and chronic health effects are discussed with appropriate examples which incorporate the above mentioned technological advances.