Acid phosphatase, alkaline phosphatase and arylsulfatase activities were determined from organic and mineral soils of a jack pine (Pinus banksiana L.) community 4 years after clear-cutting alone, clear-cutting followed by prescribed burning and clear-cutting followed by scarification. Controls consisted of uncut plots. Prescribed burning lowered soil enzyme activities in the organic layers as compared to the other treatments. Acid phosphatase activity correlated with pH, log of fire intensity, consumption of total surface fuels and consumption of total fuels. Acid phosphatase was also inversely related to soil pH. The results suggest that acid phosphatase activity may be useful for assessing the impact of fire on soils. The use of soil enzymes to predict post-fire changes in soil quality and subsequent ecological phenomena is also discussed.