Technical Abstract: Reuse of saline drainage water is a management option on the west side of the San Joaquin Valley (SJV) of California that is necessary for reducing the volumes of saline drainage that require disposal. A potential limitation to the use of these waters for agricultural production is the extent by which boron, a naturally-occurring trace element, affects the selection, growth and yield of crops in the reuse system. Boron is a concern for several reasons. First, boron is a microelement that is essential for crops, but has a small concentration window between deficiency and toxicity. Second, it has a higher affinity to soil than most common salts and requires much more water to reduce soil B than it does to reduce the salinity. Furthermore, the B concentration in SJV drainage water varies widely, but in nearly all cases, far exceeds levels that would result in toxic conditions based on B-tolerance guidelines. Confounding the interpretations of salinity-boron interactions is the influence of the pH of the soil solution. Substrate pH is known to affect B availability in soils and boron-ion relations in soils and plants. An experiment was conducted in a 24-unit volumetric lysimeter system at the USDA-ARS George E. Brown Jr. Salinity Laboratory, Riverside, CA. The test crop was cucumber (Cucumis sativus L. variety 'Seminis Turbo hybrid). Treatments were: two salinity levels (3 and 8 dS/m), three boron concentrations (0.7, 5, and 8 mg/L) and two pH levels (6.5 and 8). Plants were harvested several times during the growing period to determine biomass production and to sample for mineral ion concentration in various plant tissues. Preliminary information indicates that plant response to treatments was influenced most by the interactive effects of boron and pH. Under slightly acidic conditions, increased B had a much more dramatic reduction in plant biomass and yield than did the same increase under slightly alkaline conditions.