The effects of moisture, pH and heat on the stability of nivalenol (NIV), deoxtnivalenol (DON) and zearalenone (ZEN) present as natural contaminants of ground maize were measured for different periods. Standard solution tests were also performed to measure pH, salt and temperature effects on NIV and DON. The solution tests showed NIV and DON to be relatively stable in buffer solutions over the pH range 1-10. Quite harsh conditions (pH 12, high salt concentration, 80 degrees C, prolonged exposure) were needed to give substantial breakdown. In the ground maize substrate, these toxins were further stabilized relative to the solution tests. NIV and DON were both reduced (range 60-100%) by treatment with aqueous bicarbonate solution at 10, 20 or 50% of the ground maize dry weight, and subsequent heating at 80 or 110 degrees C for 2 and 12 days. There was no measurable reduction at lower test temperatures (20, 40 degrees C). NIV (but not DON) also showed some reduction following addition of water and heating at 80 or 110 degrees C for 12 days. ZEN content was not reduced even by 12 days of heating at 110 degrees C after treatment with a sodium bicarbonate solution.