A patented process to produce and purify large amounts of cytochalasin B is described. The fungal microorganism, Phoma exigua var. heteromorpha, is grown on a solid medium, constituted by autoclaved wheat kernels. The fungal culture, obtained growing the fungus in optimized environmental conditions, is extracted by organic solvent, to obtain crystalline cytochalasin B, in more than 3 g/kg of dried wheat culture. The advantages of this process are : production higher than that obtained with other known processes; lower production expenses; lower quantities of solvents; exclusion of chromatographic purifications. Moreover, the production of large amounts of cytochalasin B allow to prepare a wide number of derivatives, with different biological activities.商?