Researchers have long been interested in how seasonal changes affect human behavior patterns. One facet of this interest involved the study of how seasonal oscillations accounted for changes in crime rates. Two dominant theories for explaining the impact of seasonal changes on crime rates were the temperature/aggression theory and the routine activities theory. An overview of these two theories were presented and a set of hypotheses on seasonal crime trends that differ between the two theories were postulated. In order to test and compare these 2 theories, crime data from 8,460 police units were extracted from the Uniform Crime Reports (UCR) for the years 1990 through 1992. Data on climate conditions were derived from the National Climatic Data Center; communities with crime data were geospatially linked up with the closest reporting weather station. Demographic data were obtained from the 1990 United States Census and the 1992 Economic Census. The use of the Latent Curve Model with a nonlinear component allowed seasonal oscillations in crime to be modeled for a large number of cities, enabling the comparison of the two distinct theories. The analysis revealed significant seasonal oscillations in crime rates during the study period. Seasonal changes in violent crime rates were predicted by both the temperature/aggression theory and the routine activities theory, but only the routine activities theory predicted the seasonal oscillations observed in property crime rates. Additionally, the higher annual rates of crime in areas with large numbers of entertainment establishments and the greater seasonal fluctuation in crime rates observed in these cities were accounted for by routine activities theory. Thus, while the temperature/aggression theory had some explanatory power regarding violent crime, the routine activities theory was able to account for seasonal changes in both property and violent crime rates. Future studies should explore the mechanisms of these theories in more depth in light of the fact that the routine activities theory was not able to account for all seasonal crime patterns. Tables, figures, notes, references