Plant productivity, phenolic profile and natural fermentation, with and without lactic acid bacteria inoculants, were investigated in olive fruit of Ascolana tenera growing under different irrigation regimes. A rainfed control and two treatments receiving a water depth equivalent to 33 and 66% of the estimated crop evapotranspiration (ETc) from the pit hardening stage and a treatment with 66% of ETc during the entire season (25 May-4 October), were tested. Olive vigour increased with irrigation, which also induced a fresh yield enhancement, mainly due to the increase in fruit size. The differences between treatments were less evident for fruit number per tree and pulp/stone ratio. The phenolic content increased in water deficit-stressed olives and differences were detected in the concentrations of individual phenolic compounds. Olive oil content and fatty acids composition appeared scarcely affected by irrigation. Values of pH, acidity, sugars, phenolic composition and microbial population were monitored during olive fermentation. Extracts of freshly harvested olive fruits exhibited significantly higher phenolic content than extracts of processed olives. The interaction of irrigation and fermentation appeared to have a significant effect on the chemical and sensory characteristics of the end product. The bitter taste of olive fruit was positively correlated with the level of total phenolics, but negatively correlated with the overall acceptability for direct consumption. The fermentation process was accelerated in the presence of lactic acid bacteria inoculants, indicating the potential use of these microorganisms as quality control markers in table olives during processing. Copyright © 2006 Society of Chemical Industry