The effects (stimulatory/inhibitory) of two representative microelements, zinc and copper, on theaerobic co-metabolic removal of trichloroethylene (10 mg/L) by the indigenous isolatePseudomonas plecoglossicidawere investigated. The strain was previously isolated from apetroleum-contaminated site using toluene (150 mg/L) as growth substrate. Differentconcentrations (1, 10¶and 100 mg/L) of microelements provided with SO42¶−and Cl¶−as the anionswere tested. The results showed the supplement of Zn2+and Cu2+at the low concentration(1 mg/L) significantly enhanced cell growth. The removal efficiencies for toluene andtrichloroethylene were also enhanced at the low concentration (1 mg/L) of Zn2+and Cu2+,compared to the higher concentrations (10 and 100 mg/L). Compared to the control withoutzinc supplement, higher concentrations of zinc (10 and 100 mg/L) enhanced the removalefficiencies for both toluene and trichloroethylene in thefirst¶threedays but showed someinhibitory effect afterward. However, the higher concentrations of Cu2+(10 and 100 mg/L)always showed inhibitory to the toluene removal while showing inhibitory to the TCE removalafter¶threedays. For both Zn2+and Cu2+, the anions SO42¶−and Cl¶−did not show significantdifference in their effects on the toluene removal. A possible mechanism for Zn2+and Cu2+toenhance the removal of toluene and trichloroethylene would be their involvement in tolueneoxygenase-based transformation processes. In addition, high concentrations of Zn2+and Cu2+ions could be removed from the liquid by the cells accordingly. The results imply a greatpotential of supplementing low concentrations of zinc and copper to enhance bioremediationof the sites co-contaminated with toluene and trichloroethylene.