Sorption studies of ponderosa pine (Pinus ponderosa Laws.) needles and litter beds of current year cast show a shorter response time and lower equilibrium moisture contents than most other conifer needle data in the literature. For conditions below fiber saturation, the response time is described best by considering the time for 95 percent of the total change in moisture content. Equilibrium moisture content can be estimated by an equation based on temperature and humidity, but type of vegetation must be considered. Analysis of moisture response at the test conditions indicates that the moisture diffusivity of the needles and beds remains nearly constant for both adsorption and desorption.