Research was conducted in 2005 at the Central Crops Research Station near Clayton NC and the Border Belt Tobacco Research Station near Whiteville NC. Ethylene inhibitor studies evaluated the effect of 1-methylcyclopropene (1-MCP) on the holdability of flue-cured tobacco in both locations. Ethylene is a natural plant hormone synthesized in the roots that is responsible for senescence in aging tissue. Ethylene is also produced in response to environmental stresses and physical damage, mainly wind and water damage. 1-MCP is an ethylene binding inhibitor that has 10 times the affinity for the ethylene-binding site than does ethylene. Once 1-MCP successfully occupies the ethylene-binding site, 1-MCP causes inhibition of the active complex and the effects of ethylene are then lost. 1-MCP was applied at 14 and 7 days pre-harvest and at normal harvest time to determine effects on holdability. Harvest treatments were imposed at normal and normal plus 10, 20, and 30 days. A specially designed crop oil used with 1-MCP was also tested at 14 and 7 days pre-harvest and at normal harvest. According to data received in 2005, no differences in holdability or grade of flue-cured tobacco were achieved when 1-MCP was compared to the control. Treatment time applications were giving as suggestions from the manufacturer of 1-MCP, Agro Fresh Inc. Applications of 1-MCP at 14 and 7 day pre-harvest were not successful in binding to the ethylene-binding site. Field observations suggest that the natural ethylene supply of the plant had already bound to the receptor site and elicited action. Based on these observations, 1-MCP must be applied at earlier dates in order for the natural ethylene supply of the plant to be inhibited. Insufficient rain accumulation also caused the crop to start the senescence process earlier than expected. In the 2006 growing season, in addition to field experiments, greenhouse applications of 1-MCP will be applied to flue-cured varieties to determine correct timing of 1-MCP application. After application, leaves will be sampled and then analyzed by gas chromatograph to determine exogenous ethylene levels.