The degradation of three types of anomalous proteins, e. g. those containing the arginine analog kanavanine; polypeptides synthesized in the presence of puromycin (100 micrograms/ml) under slight inhibition of total translation, and polypeptides synthesized under amino acid deficiency, was studied. In order to measure the rate of proteolysis, the E. coli cells were labelled for 5 min with [14C]-phenylalanine and then transferred to a complete medium. The loss of TCA-insoluble material was taken as a measure of proteolysis. While the normal total protein of E. coli cells was degraded at the rate of 2--8% per hour, the canavanine-containing proteins were degraded at the rate of 30--40% per hour. The polypeptides synthesized in the presence of puromycin were degraded at the rate of 10--15% per hour, while the polypeptides formed under amino acid starvation--at the rate of 7--8% per hour. The rate of proteolysis of canavanine-containing polypeptides was two times lower under inhibition of translation by chloramphenicol, tetracycline of kasugamicin, while the rate of degradation of two other types of anomalous polypeptides was significantly increased. Tetracycline at concentrations significantly exceeding those sufficient for maximal inhibition of translation, practically completely repressed the proteolysis of canavanine-containing proteins. No such tetracycline activity was observed in the presence of 20 mM Mg2+, which was assumed to be dependent on the complexon-forming ability of the antibiotic.