The use of agricultural soils to recycle sewage sludge (SS) is especially limited on acid soils like those existing in the northwest of Spain. An experimental design was laid out in order to quantify the effects of several rates of SS on soil chemical properties, total and exchangeable heavy metals and absorption by an indicator plant in two representative soils. Soil acidity increased with applications above 50 Mg ha^-1 SS as detected on soil pH KCI and on the saturation of exchangeable complex by aluminum. No direct response to SS was observed on the total metals whereas DTPA extractable nickel and zinc increased progressively with the increasing doses, and copper was above average. Phosphorus, copper, nickel and zinc contents in vegetative tissue were related to soil levels and to the rates of SS supplied, increasing significatively for doses higher than 50 Mg ha^-1. It is advisable to check soil acidification; extractable copper, zinc and nickel as this reflects actual bioavailability; and ensure whether bioaccumulation takes place by the analysis of an indicator plant.