The study describes the sorption of Cr, Cu, Mn and Zn by Pseudomonas aeruginosa AT18 isolated from a site contaminated with petroleum and heavy metals. The concentrations studied (mgL-1) were Cr-50, Cu-49, Mn-60 and Zn-70. The solution pH and ionic strength were very important factors in the metal biosorption performance and the biosorption capacity of Pseudomonas aeruginosa AT18 for Cr3+ Cu2+, Mn2+ and Zn2+. In aqueous solution the biosorption increased with increasing pH in the range 5.46-7.72. The results obtained in the experimental assays show that Pseudomonas aeruginosa AT18 has the capacity for biosorption of the metallic ions Cr3+, Cu2+ and Zn2+ in solutions, although its capacity for the sorption of manganese is low (22.39 mg Mn2+/g of biomass) in comparison to the Cr3+, Cu2+ and Zn2+ ions, as shown by the individual analyses. However, 20% of the manganese was removed from an initial concentration of 49.0 mgL- 1, with a Qm value similar to that obtained in solutions containing mixtures of Cr3+ Cu2+, Mn2+ and Zn2+. The chromium level sorbed by Pseudomonas aeruginosa AT18 biomass was higher than that for Cu, Mn and Zn, with 100% removal in the pH range 7.00-7.72 and a Qm of 121.90-200.00 mg of Cr3+/g of biomass. The remove of Cr, Cu and Zn are a result also of precipitation processes.