Abstract Culture conditions, plating density, and ventilation govern the production of fruiting bodies in Phycomyces, both regular sporangiophores (macrophores) and dwarf ones (microphores). Massive microphorogenesis is observed after flooding 48-h-old mycelia with water or a water gel and incubating them further in the dark. The resulting spores are easily transferred with sterile toothpicks; this facilitates the repetitive subculturing required in many genetic experiments. Microphorogenesis is stimulated by increased carbon dioxide concentrations, but is largely unaffected by variations in oxygen content of the atmosphere. Cyclic AMP at high concentrations inhibits all phorogenesis; dibutyryl cAMP at the same concentrations inhibits microphorogenesis, but not macrophorogenesis.