The objective of this study is to introduce a new procedure to determine the impact of climate on human mortality with the use of a synoptic climatological approach. The holistic nature of synoptic categories allows for the simultaneous evaluation of numerous weather elements as they realistically appear within air masses. In addition, this approach allows for a better distinction between pollution-induced mortality and weather-induced mortality. A synoptic categorization was performed for St. Louis, Missouri, and each category was evaluated in terms of its mean daily mortality. Of 10 summer categories found in St. Louis, one possessed the highest mean mortality by far, and 8 of the top 10 mortality days in St. Louis occurred when this category was present. Further analysis determined that long, consecutive day periods of this hot, oppressive category are associated with a continuing rise in mortality. It was determined that the procedure described here has the potential to be used in a weather/mortality watch-warning system. Finally, it appears that day-to-day mortality fluctuations are much more sensitive to weather than to pollution concentrations, as the oppressive category associated with the greatest mortality possessed levels of six major pollutants that were not noteworthy.