Researchers are increasingly interested in the potential of accelerometers to improve our ability to measure and understand the health impacts of physical activity. Although accelerometers have been available commercially for more than 25 yr, broad consensus about how to use these tools has not been established. At a scientific conference in December 2004, a number of scientists were invited to present papers, serve as reactors or moderators to papers, present posters of original research, or serve as members of an audience knowledgeable about the use of accelerometers. During 2½ d, information about best practices of accelerometer use was presented and suggestions for future research were made. From the collective experience of papers presented and discussions held, five areas of accelerometer use were described. This paper summarizes the best practices and future research needs from those five areas: monitor selection, quality, and dependability; monitor use protocols; monitor calibration; analysis of accelerometer data; and integration with other data sources. Suggestions for reporting standards for journal articles also are presented.