Ixodes scapularis (Say) is the vector for Borrelia burgdorferi (Bb) the causative agent of Lyme disease (LD). The increased number and presence of ticks in the environment pose a significant health risk to people and many domestic animals including dogs, cats, and horses. This study characterized the distribution and expansion of I. scapularis and Bb and identified areas of increased risk of LD transmission in Indiana using geographical information systems (GIS) and spatial analysis. A cross-sectional sampling was performed for 3 consecutive years (2005-2007). A total of 3,412 harvested white-tailed deer (Odocoileus virginianus) were searched for ticks at Department of Natural Resources manned deer check-in stations. Hunters were asked for verbal permission to search the deer and to indicate on a road atlas where the deer was killed. All deer points were digitized into a GIS database. Identification of clustering in space and time for these organisms was performed using geostatistical software. Multiple spatial clusters of I. scapularis-infested deer were identified in western Indiana. B. burgdorferi was isolated from tick pools in 11 counties. In addition to the I. scapularis clusters, one spatial cluster of Bb-infected ticks was identified. Our current survey results and cluster analysis indicate that the western geographic regions of Indiana should be considered by the healthcare community to be at increased risk of LD compared with the rest of Indiana.