Fil: Canteros, Cristina. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Microbiologia; Argentina.Fil: Rodero, Laura. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Microbiologia; Argentina.Fil: Rivas, María Cristina. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Microbiologia; Argentina.Fil: Davel, Graciela Odelsia. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas. Departamento de Micología; Argentina.A rapid method to evidence urease activity is described. Urea hydrolysis and consequent production ammonia are detected by a chemical reaction producing a blue phenol compound (indophenol blue). Three hundred and three yeast were tested. Out of 107 urease-positive organisms detected by Christensen's Urea Agar Test (CUAT) 102 were positive by our method. No false negatives were observed by this method when testing 87 Cryptococcus strains. Ths practical screening test for presumptive identification of Cryptococcus neoformans is simple, unaffected by pH changes and requires 15 minutes to be performed.