The production of coagulase, DNase and haemolysins by 30 L-forms obtained from as many strains of Staphylococcus aureus having these properties, has been studied using different techniques. All of L-strains produced coagulase, for the most part after incubation for 24 h, but only some produced DNase and haemolisins. At the same time, the sensitivities of various antibiotics of staphyloccal L-forms and the parent strains has been determined. All of L-forms, as regards to bacterial form from which they were derived, showed an high resistance to antibiotics of which the primary site of action is upon cell wall (penicillin, ampicillin, methicillin, cephalosporins, vancomycin), with the exception of bacitracin. The tetracycline was more effective against the L-forms, while the group that includes chloramphenicol, novobiocin, streptomycin, gentamycin and kanamycin inhibited coccal and L-forms about equally.