Three mixed cultures of aerobic bacteria were able to grow on 6-aminocaproic acid polyamides of low molecular weight (1400, 2100, 6800) as the only carbon and energy source. No growth was absorbed on polyamide of a molecular weight of 11000. Growth was accompanied by the utilization of cyclic and linear oligomers of up to eight manomeric units present in the polymeric matrix. The extent of the growth was higher on polyamides at lower molecular weight and depended on the amount of oligomers utilized.