Deer tick vectors of Lyme disease spend most of their life close to the soil surface. These ticks generally dehydrate quickly when not in close proximity with soil and other sources of moisture. However, little is known about how soil moisture affects tick host-seeking activity and mortality. Laboratory and field studies were conducted to determine a soil moisture threshold level at which ticks cease host-seeking activity. During a laboratory study conducted under controlled moisture and temperature conditions the behavior of ticks added to undisturbed soil cores (5 cm –long, 5 cm-dia.) was only affected at low volumetric moisture (<2%). This result was corroborated by a field experiment in which undisturbed forest soil mesocosms (20 cm-dia) were allowed to dry under rain-tight canopies. Tick host-seeking activity did not appear to be affected by soil moisture levels, which were higher than in the laboratory experiment (>4% by volume). A third experiment conducted in 6 forested field sites where soil moisture never fell below 13% confirmed that soil moisture alone may not be a determinant of tick activity in natural forested sites since soil moisture levels rarely reach this tick's soil moisture activity threshold. Explanations for tick population declines typically observed in response to drought or drying conditions may include factors other than soil moisture that affect the tick's ability to re-hydrate at the soil-leaf litter interface.