summary. Plateletpheresis donors will lose up to 100 mL of blood at each donation, leading to concern that they may become iron deficient, particularly if donating at the maximum allowed frequency under National Blood Service policy of every 2 weeks. The serum ferritin levels of 508 regular plateletpheresis donors and 101 non-donors were measured to indicate the level of their iron stores. About 33·9% (156/460) of platelet donors had depleted iron stores compared with 3·1% (3/97) non-donors. Results for male and post-menopausal female donors were similar with 36·2% (131/362) of males and 37·7% (20/53) of post-menopausal females showing iron depletion. There was clear correlation with donation frequency in males with 63·9% (46/72) of males donating at 2 weekly intervals found to be iron depleted. The percentage of iron depleted male subjects decreased as donation intervals increased. Correlation with lifetime donations of platelets was not demonstrated, although no donor who had given fewer than 14 blood and/or platelet donations was found to be iron depleted. In males there was a clear correlation between iron depletion and frequency of donation. There appeared to be no correlation with lifetime number of platelet donations. As a result of this study, we have advised that volunteers should not donate platelets more than 15 times per year, so that red cell loss is no more than the equivalent of three whole blood donations (1500 mL).