The effects of 'alperujo' compost on trace element availability and on microbial activity of two contaminated soils, a calcareous soil (S1) with high contents of Pb and Zn, and an acidic soil (S2) with a substantial amount of Al, As, Pb and Zn, were assessed. Additionally, the growth and capacity for contaminant phytoextraction of five Brassica species were studied. Compost amendment did not affect S1, but in S2 it increased soil pH, thus reducing Al and Zn bioavailability and toxicity. Compost application also increased microbial population and bioactivity in both soils. Brassica plants did not survive in S2, yet they thrived in S1. When compost was applied to S2, Brassica carinata, Brassica napus and Brassica oleracea grew adequately. Considering both the capacity to accumulate trace elements in the shoot and the ability to grow in the contaminated soils tested, the most efficient phytoextractors were Brassica juncea in S1 (particularly for Zn) and Brassica oleracea in S2 (for Al, As, Pb and Zn).