Data were based on interviews with approximately 114,000 persons aged 12 and older living in 54,000 households. Based on total victimizations, the highly seasonal crimes were household larceny of $50 or more, rape, household larceny of less than $50, and unlawful entry. Crimes with the least amount of seasonality were personal larceny with contact involving $50 or more, motor vehicle theft, robbery, forcible entry, and simple assault. Generally, the amount of seasonality observed for a particular offense type was similar for both reported and unreported offenses, with notable exceptions such as simple assault and forcible entry. Where there were differences, reported crimes tended to be more seasonal. The usual seasonal pattern was for the high-crime months to be in the summer and the low-crime months to be in the winter. Significant exceptions to this pattern were robbery and personal larceny with contact, which peaked in December. Crimes with the same degree of seasonality may have had different month-to-month patterns. 5 tables, 8 figures, and technical appendix.