Fifteen sites in 4 different vegetation types in a Lyme disease endemic area were surveyed during times of peak tick activity in fall of 1982, 1984, and 1992, and subsequent spring activity periods to determine seasonal and year-to-year differences in habitat use by the blacklegged tick, Ixodes scapularis Say. Populations of I. scapularis adults varied significantly among the 3 yr surveyed, although this variability tended to be more pronounced in fall. I. scapularis adults were consistently more abundant in the fall than spring. Significant seasonal and year-to-year differences in adult populations were observed between and within vegetation types. However, the variability in habitat use was generally lower in spring compared with fall. In most of the surveys, the 5 sites yielding the greatest number of adults were represented by 3 or 4 of the vegetation types. Explanations for this variability and implications for tick surveillance and reducing risk of Lyme disease transmission are discussed.