Abstract: The objective of this study was to investigate the effect of Nitric Oxide (NO) on the production of basal and wound-associated stress ethylene (C₂H₄) from intact and fresh-cut tomato fruits, respectively. For this purpose, a non-invasive and online sampling technique based on Laser Photoacoustic Spectroscopy (LPAS) was employed. Pre-treatment of intact Mature Green (MG) tomato fruits with a low concentration (200 ppbv) of NO gas resulted in a significant and steady average reduction of 33% in the basal-level C₂H₄ production to 6.0±0.44 pmol h^-1 g fwt^-1 compared to 9.0±0.18 pmol h^-1 g fwt^-1 in the non-treated MG control. Moreover, NO gas fumigation of fresh-cut MG tomato fruit slices caused a 60% reduction in peak wound-induced C₂H₄ levels compared to untreated fresh-cut control fruit. These results clearly indicate that NO pre-treatment negatively impacts on both basal and wound-associated stress C₂H₄ emission levels, respectively in both intact and fresh-cut tomato fruits. These results are discussed in the light of possible mechanisms of NO interference with C₂H₄ biosynthesis. Moreover, the potential utilization of NO in controlling stress-induced and undesirable biochemical changes which are known to occur in fresh-cut fruits is highlighted.