An investigation has been performed with a new parenteral iron preparation, iron-poly-(sorbitol-gluconic acid) complex (Ferastral) in the treatment with iron deficiency anaemia associated with inflammatory diseases, mainly rheumatoid arthritis. Fifteen moderately anaemic patients entered into the trial. These patients constituted a special group in whom the MCHCs were subnormal. Observations were made concerning the occurrence of side-effects. Particular attention was paid to those-side-effects which are known to be associated with the use of parenteral iron preparations in the treatment of rheumatoid subjects. Ferastral was administered by intramuscular by intramuscular injection. The single doses given on any one occasion varied from a minimum of 100 mg to a maximum of 500 mg, divided into two separate injections. The results of therapy, measured at eight weeks, showed significant increases in haemoglobin concentrations. Increases in erythrocyte count, MCHC and serum-iron concentration were also found. There were no signs of acute toxic effects with Ferastral and in no patient was there exacerbation of arthritis as has been previously reported with iron-dextran.