Technical Abstract: Many sampling projects have been initiated in recent years to determine the effectiveness of various best management practices in protecting water quality. Although comprehensive references on discharge data collection have been published, similar guides to water quality sampling are not available. As a result, compilation of available information on the design of water quality sampling projects is needed so that proper decisions can be made regarding data collection resources, procedural alternatives, and project goals. Thus, the objective of this manuscript is to compile and present the state-of-the-art methodology for collection of discharge and water quality constituent data to support BMP evaluation in terms of water quality effects. Although many considerations are involved in establishing a successful sampling project, the following recommendations are generally applicable: 1) assemble a well-trained, on-call field staff willing to make frequent site visits, 2) commit adequate resources for equipment maintenance and repair, 3) establish reliable stage-discharge relationships for accurate discharge measurement, 4) use periodic manual grab sample collection with adequate frequency to characterize baseflow water quality, 5) use flow-interval or time-interval storm sampling with adequate frequency to characterize storm water quality, and 6) use composite sampling to manage sample numbers without substantial increases in uncertainty.