The purpose of this work was to study how the type of post-harvest process, i.e. natural preparation known as the dry method, and two wet processes, affected contamination and toxin production up to the green coffee stage. Batches were contaminated with ochratoxin A or with OTA-producing strains of Aspergillus ochraceus and Aspergillus niger. For OTA artificial contamination, hulling or husk removal caused a reduction of OTA. When A. ochraceus was inoculated at low level, its growth was hampered by indigenous mould flora contrary that observed with A. niger. The fungal counts and OTA assays showed that the best way of limiting the development and impact of contaminating toxigenic flora "from the field" was the physical wet method.