Growth parameters and Fe, Cu, Mn and N status ofEuglena graciliscells were determined as a function of level and source of Fe supply in the nutrient environment. Use of FeEDDHA promoted cell division while FeSO4·lb7H2O promoted cell enlargement after 7 days. Greatest N content was present in rapidly dividing as compared to enlarging cells. Copper content was directly related to cell size with larger cells containing more Cu than smaller cells. Manganese uptake was inversely related to Fe supply with FeSO4·lb7H2O inhibiting Mn uptake to a greater extent than chelated Fe. Iron uptake increased significantly with the addition of iorganic or chelated Fe. The Fe uptake was comparable from both sources at the 1 ppm Fe level of supply, but much greater amounts of Fe were accumulated from inorganic supply at the 10 ppm Fe level.