The influence of a sewage sludge compost on the chemical and physical properties of an Ultisol and a Mollisol of Puerto Rico were evaluated. Treatments evaluated were: Control (0 compost), 15, 30, 45 and 180 tons/acre of compost. Cassava plants (Manihot esculenta - PI 12902) were planted to ascertain the effects of the compost on crop performance and trace element uptake. The compost behaved as an acid neutralizing agent, raising the pH of the Ultisol from 4.2 in the control to 7.5 in the uppermost treatments (> 30 tons/acre). Such a significant influence on pH was attributed to the high calcium content of this compost, a reflection of the coagulating agent (Ca(OH)2) employed in the treatment plant. Significant increases were also observed for soil electrical conductivity, phosphorus (Olsen), and levels of EDTA- and DTPA-extractable Fe, Zn, Cu, and Cd. Trace element content remained well below EPA standards (EPA 503 rule). Cassava yield estimates based on 4 month old plants suggest that although beneficial effects may be expected in both soils at moderate rates, excessive loading may be deleterious to crop growth presumably due to overliming or salinity problems.