The spatial distribution of larvalIxodes damminiSpielman, Clifford, Piesman,&Corwin was examined at two sites in Westchester County, N.Y., an area endemic for Lyme disease. Larval abundance peaked in early August and was marked by a highly clumped distribution reflecting high concentrations of newly hatched larvae. Subsequent sampling indicated an increasingly uniform distribution of larvae as measured by the variance/mean ratio and Lloyd's index of patchiness. An experiment using ticks marked with fluorescent powder to illustrate the degree of active dispersal (tick disperses by its own movement) indicated little lateral movement; only 3 (4%) of the 77 marked larvae recovered during the experiment were found beyond 3 m from the release point. The recovery of unfed larvae (12 larvae [0.6% of total] were recovered from raccoons,Procyon lotor(L.); 9 [3.4%] from mice,Peromyscus leucopusRafinesque; and 32 [9.0%] from opossums,Didelphis virginiana(Kerr)) from captive hosts in the laboratory suggests that passive transport of unfed larvae may be a mechanism of dispersal.