Our objective was to determine the optimal irradiance, total N concentration, and NO3--N:NH4+-N ratio for greatest edible biomass production of three cultivars of basil (Basilicum ocimum L.) in a controlled-environment production system. Preliminary experiments showed basil required a dark period, but the duration of the dark period was not resolved. Based on our results, canopy-level irradiance should not exceed 500 mumol/m2/s to conserve energy while enabling the greatest edible biomass production of basil in a controlled-environment production system. Optimal edible biomass production occurred at 100 to 250 mg N/L at a ratio of 50:50 nitrate-N : ammonium-N. All plants died in the 100% ammonium-N treatment. Regression models that allow analysis for optimum conditions suggest a nitrate-N : ammonium-N ratio of 50:50 to 75:25 yielded the greatest biomass of basil.