Aspen (Populus tremuloides) are in decline throughout the interior western U.S. because of conifer invasion, fire suppression, and overbrowsing by domestic livestock and native ungulates. Aspen restoration requires disturbances such as fire or cutting and exclosures to protect against overbrowsing. We measured the effects of the 1996 Pole Creek fire, Fishlake NF, UT on soil N mineralization/immobilization during the summer of 1997 using an ion exchange membrane (IEM) soil core incubation method. Two incubation periods were used: 6/25 to 7/22/97 (27 d) and 7/22 to 9/23/97 (63 d). Net soil N mineralization/immobilization rates in unburned aspen and unburned mixed aspen/conifer areas were very low. Amounts of NH4 and N03 accumulated by IEM's and in soil cores were significantly higher in the burned aspen/conifer area than in unburned areas. More NH4 was accumulated in the IEM's and soil cores during the first incubation, whereas more N03 was accumulated in the IEM's and soil cores during the second incubation indicating an increase in nitrification as summer progressed. Even though more soil cores in the burn area had higher rates of mineralization or immobilization than those in unburned areas, net mineralization/immobilization rates in the burn area one year after the fire were not significantly different from unburned areas because of the balance of the two overall processes. The increased amounts of soil NH4 and N03 as a result of fire provide a source of N for aspen regrowth until N mineralization/immobilization in I leaf litter can again become the dominant process of N cycling in the aspen ecosystem.