The influence of one-and two-sided regulated atmospheres with lower 02-and increased CO2-concentrations in comparison with air was studied on the growth and toxin-production of 4 different mycotoxin-producing molds (A. versicolor, P. expansum, P. urticae, B. nivea). Low O2-values in the atmosphere (2-0.5%) had scarely an influence on the development and toxinproduction in different nutrient media after 14 d at 25 degrees C. Only higher CO2-and lower O2-concentrations than that of the air (e.g. 40% CO2, 6% O2) reduced the sterigmatocystin-and patulin-production in nearly all cultures, whereas growth was only retarded insignificantly. Atmospheres with 90% CO2 and 10% air as well nitrogen atmospheres with 10% CO2 inhibited remarkably the growth of molds and prevented the toxin-production of nearly all strains. In pure N2-atmospheres most of the A. versicolor strains exhibited growth with toxic mycelia whereas only minimum growth of the patulin-producing species without any patulin synthesis had been observed.