In summary, in the collection, analysis, and interpretation of study data, individuals planning and analyzing the results of their own investigations or those of others must be particularly careful about the potential pitfalls that may occur. Considerable time and effort beforehand should be given to the type of study design (observational versus randomized trial) to be utilized; the scope of the investigation to be carried out, be it of a small descriptive scale or a large collaborative effort; attention to detail in the development of the data-collection instruments; and extensive training and continued monitoring of the data abstractors. Awareness of these factors should enhance data collection efforts, the quality of the collected data, and any interpretation thereof.