Sporulating cultures of Cercosporazeae-maydis were obtained routinely by homogenizing freshly isolated or stored cultures in waterdispensing the homogenate on V-8 juice agar, and incubating the plates under a diurnal fluorescent light regime for 14 days. Sporulation was good on decoction media made from green or senescent corn leaves and on V-8 juice agar but was poor on potato-dextrose agar. Constant light inhibited conidial germination, mycelial growth, and sporulation. The optimum temperature range for germination and growth was 22-30 C. Cultures of the fungus could be stored successfully for at least 23 mo at 4 C on several media. Lesion development on corn plants was obtained by misting inoculated plants for 3sec every 4 min between the hours 2000 and 1000 each day for 2 wk. Lesion development in the greenhouse was greater from June through August, when the greenhouse was kept at 22-28 C by wetpad cooling, than during the other months.