A protocol is presented for the production of Lagenidium giganteum, a fungal pathogen of mosquito larvae, using a two-phase system consisting of aqueous extracts of sunflower seed in liquid medium and in solid agar-base medium. The cultures on solid medium are applied in the field and may be stored for up to 12 weeks at 15-16oC. Suggestions are made for field use and evaluation of the fungus for mosquito control. Directions for media preparation and quality control are included.