A field trial and a greenhouse experiment were conducted to investigate the impacts of N and K nutrients on plant N/K assimilation, nitrate reductase activity (NRA), curd yield and quality of cauliflower cv. ‘Minuteman’. In the field study the treatments consisted of five N rates (0, 55, 110, 165 and 220 kg/ha) and three K rates (0, 25 and 50 kg/ha). In the greenhouse study the treatments were five levels of N (0, 16.5, 33, 50 and 66.5 mg/plant/day) using a modified Hoagland nutrition solution. In the field study the interaction of N/K rates was significant in cauliflower whole plant N/K uptake. Head N/K accumulation was 32-35% of plant total N/K uptake (8.0 g/plant), which was significantly correlated with head yield and size (P<0.05). Cauliflower NRA was associated with leaf/head sap NO3-N concentrations. It is suggested that nitrogen and potassium translocation is an important factor of cauliflower yield and quality.