The influence of different parameters on the sporulation of Metarhizium flavoviride was studied during submerged cultures in shake flasks and in 5 l bioreactors. The screening in shake flasks of several carbon and nitrogen sources allowed the definition of an optimal medium, based on sucrose and brewer’s yeast with a C/N ratio of 1.6. With this medium, a production of 5.4 _ 108 blastospores per ml (Bspores ml_1) was obtained after 169 h of cultivation. The influence of pH and pO2 was independently studied in 5 l working volume bioreactors using the optimal medium. The best production was obtained with pH and pO2 regulated respectively to 7 and 100%. Finally, when the culture was grown under optimized conditions, the blastospores concentration increased 16-fold, with 1.1 109 Bspores ml-1 obtained after 144 h cultivation. This represents a gain of productivity of about 4.8 times