As a step of a doctoral research project, in this study a live-type nosode was prepared from microorganism Mycoplasmagallisepticum strain R (ATCC 93-08/19610) according to Costa model and the rules by Brazilian Homeopathic Pharmacopoeia. Live nosode was tested in vitro to assess safety when used to immunize domestic fowl (Gallus gallus) against infection by this microorganism and to investigate its behavior under laboratory conditions. M. gallisepticum was not shown to grow in fluid (broth) and solid (plate) modified Frey medium with dilutions 11d, 12d, 20d and 30d. Inhibition halos about 2.0 mm were observed around paper disks impregnated with live-type nosode in microorganism-sown Petri dishes, whereas disks impregnated with conventional antibiotic oxytetracycline exhibited 8.0 mm inhibition halos. Protein assessment by Folin-Lowry method showed protein absence in dilutions 12d and 30d and neither microbial DNA traces were found in PCR assay in dilutions 12d, 20d and 30d.