Seventy-three bacterial isolates from polluted streams as well as 157 of their heavy metal-tolerant (HM-tolerant) derivatives were tested for their sensitivity to ampicillin, ticarcillin, gentamicin, cephalexin, sulfamethoxazole, tetracycline and colistin. Among the parent strains 19% were sensitive to all antibiotics tested and 70% were multiple resistant. The mean resistance of parent strains was 227 antibiotics per isolate. Mean resistance was increased to 2.82 for silver-, 3.32 for gold-, 3.48 for copper-, 3.78 for nickel-, and 3.79 for cadmium-tolerant subcultures. A statistically significant increase in resistance was demonstrated for tetracycline and sulfamethoxazole in all HM-tolerant subcultures, for cephalexin in gold-, nickel-and cadmium-tolerant strains, for ampicillin in gold-tolerant isolates and for ticarcillin in cadmium-tolerant strains.