We describe here the protocols followed by CIMMYT at the MLN Screening Facility, Naivasha, Kenya, for culturing and increase of inoculum for MLN-causing viruses (MCMV and SCMV) in eastern Africa, followed by phenotyping of maize germplasm against MLN (under artificial inoculation with MCMV + SCMV) or for individual viruses (MCMV or SCMV) under controlled (nethouse) conditions.