Lettuce seedlings were grown in pots on Aeric fulvaguents, added with lime (pH= 7.55) and without lime (pH= 6.52). Metals were sprayed to soil at a rate of either 2.5 mg Cd kg-1 soil or 50 mg Zn kg-1 soil, or as a combination when plants were one month old. Successive additions were made at a rate of five- and ten-fold after two and four weeks of initial application, respectively. One week after each metal application, rhizosphere soil was analyzed for respiration, substrate induced respiration (SIR) plate counts of bacteria, fungi, Cd and Zn resistant fungi, pH and DTPA extractable metal. Plants were assessed for mycorrhizal infection and tissue P and metal contents. Soil respiration decreased following ten-fold application of metals but SIR showed a significant reduction following each metal application except for the first application to limed soil. Combined metal treatment resulted in a reduction of bacterial populations by 98% and 52% in non-limed and limed soil, respectively. Fungi declined by 50% following application of five-fold high Zn and Cd into non-limed soils but no difference was observed after adding ten-fold high doses to the limed-soil. As Cd dose increased by ten-fold, percentage of Cd resistant fungal populations increased from 25% to 32% and from 14% to 75% in non-limed and limed soil, respectively. In non-limed soil, mycorrhizal infection and plant growth declined drastically following application of 25 mg Cd and 500 mg Zn. In non-limed soils, extractable Cd correlated with bacteria (r = -0.54), fungi (r = -0.47), Cd-resistant fungi (r = 0.80) and mycorrhizal vesicles (r = -0.48) whereas in limed soil, with respiration (r = -0.57) and Cd-resistant fungi (r = 0.81). Added metal doses were more toxic on mycorrhizae and lettuce at a pH of 6.5 but less significant at pH of 7.5.