Studies were conducted to determine the effect of irrigation regime on yield and nitrogen recovery of field grown lettuce in the Bekaa Valley of Lebanon, under non limiting soil N conditions. Within the experimental plots, irrigation differentiation was made upon crop evapotranspiration (ETc) measured on a non-weighing lysimeter of 16 m². The treatments included a control, I-100, irrigated at 100% of ETc, and two water deficit treatments, I-80 and I-60, irrigated at 80% and 60%, of ETc, respectively. Prior to planting, all plots received fertilizers broadcast at a rate of 250 kg ha -1 of NPK-fertilizer (17%). At 6-leaf and 12-leaf stages, ammonium nitrate (34.5%) was applied with irrigation water in two applications of 125 kg ha -1 each. Local groundwater containing 10 mg l -1 N-NO 3 was used for irrigation. Yield was determined in a final destructive harvest. Crop evapotranspiration reached on the lysimeter a total of 433 mm for a total growing period of 70 days. Results showed that water stress caused by the deficit irrigations significantly reduced leaf number, leaf area index and dry matter accumulation (p<0.05). Water deficit also reduced final fresh weight by 20% to 30% with comparison to the control. Nitrogen recovery reached 218 kg N ha -1 at maturity as compared to control, while consistent reductions averaging 35% and 40% were observed on I-80 and I-60, respectively. Nitrogen use efficiency (NUE) also decreased markedly in to the less irrigated treatments. Finally, it could be concluded that nitrogen inputs from groundwater was considerable as a component of the soil nitrogen balance and increased the potential of N loss with leaching as a source of point pollution.