Skeletal muscle actin was found by centrifugation, turbidity, and viscosity measurements to form polymers upon addition of aminoglycosides, viomycin, polymyxin B, and tetracycline. A linear relationship was observed between the amount of actin polymerization and the number of primary amino groups on the aminoglycoside antibiotics except kanamycin. Of the antibiotics studied, neomycin was most efficient in actin polymerization. Polymerization of actin was not significantly induced by kasugamycin, chloramphenicol, erythromycin, benzylpenicillin, angustmycin A, formycin, actinomycin D, and mitomycin C. Aminoglycosides and viomycin were demonstrated to inhibit the acto-HMM Mg(2+)-ATPase reaction but did not significantly affect HMM Mg(2+)-ATPase activity. It was found by equilibrium dialysis that [(3)H]dihydrostreptomycin bound to actin.