Modifications were made of Papavizas' VDYA-PCNB medium that increased its selectivity for Thielaviopsis basicola.  Glucose was omitted, chloramphenicol and penicillin were substituted for streptomycin and chlortetracycline, and the concentrations of nystatin and PCNB were increased.  These changes resulted in increased recovery of T. basicola from artificially or naturally infested soils, in reduced numbers of bacterial and fungal contaminants, and made possible enumeration of T. basicola in soil amended with plant residues.  The modified medium contained, per liter, 200 ml V-8 juice, 2 g yeast extract, 20 g agar, 1 g pentachloronitrobenzene, 1 g oxgall, 50 mg nystatin, 250 mg chloramphenicol, and 60 mg K penicillin G.  The pH was adjusted to 5.2.  Carrot root extract was suitable as V-8 juice as a base for the medium.