Nitrate Reductase activity (NRA) was detected in the blueberry cultivars (Vaccinium sp.), ‘Bluecrop’ and ‘Tifblue.’ Shoots treated with KNO3 induced the highest level of NRA in leaves and stems of both cultivars. In ‘Bluecrop’ and ‘Tifblue,’ the older leaves showed higher NRA compared to young leaves. Aluminum and sulfate ions and various forms of NH4 + showed an inhibitory effect on NRA in both cultivars. NRA in younger leaves was more sensitive to the addition of various ions than in the older leaves, and ‘Bluecrop’ NRA was more sensitive than ‘Tifblue’ NRA. Cytokinins (kinetin, zeatin, zeatin riboside and 6-benzylaminopurine) supplemented with nitrate showed an additive stimulation of NRA under light and dark. However, under light, the level of NRA in blueberry induced with cytokinins was much greater than that obtained in the dark. [Article copies available from The Haworth Document Delivery Service: 1-800-342-9678.1