Background/Aims: Intravenous immunoglobulin (IVIG) therapy has been associated with renal adverse effects and electrolyte disturbances. Methods: We retrospectively evaluated a cohort of 66 unselected patients with idiopathic thrombocytopenic purpura, who received 140 courses of IVIG therapy. Acute renal failure (ARF), hyponatremia and hyperkalemia, as potential complications of IVIG therapy, were assessed from 100 IVIG courses with sufficient data for analysis. Results: Thirteen out of 100 (13%) IVIG courses in 10 (15%) patients were complicated with ARF. Risk factors included advanced age, pre-existing renal impairment, use of diuretics and the presence of diabetes mellitus. All patients recovered renal function 1–2 weeks after IVIG infusion. Serum sodium (sNa) fell by 5.7 and 2.7 mmol/l (p < 0.01) in patients with and without ARF, respectively. Correspondingly, serum potassium increased by 0.7 and 0.23 mmol/l (p < 0.01). There was a strong inverse correlation (r = –0.308; p < 0.01) between changes in sNa and creatinine. Changes in serum potassium could be independently predicted by changes in both sNa and creatinine (R<sup>2</sup> = 0.11; p < 0.01). These data suggested that both hyponatremia and hyperkalemia were (a) due to the translocational effect of the osmotic load of sucrose, and (b) largely depended on the extent of IVIG nephropathy. Conclusion: In our series, ARF attributable to IVIG therapy, although not rare, was usually mild and fully reversible. High-risk patients were more susceptible to IVIG-related renal complications. Translocational hyponatremia and hyperkalemia following IVIG therapy, although unimportant in patients with normal renal function, may be of clinical significance in patients with severely compromised renal function, resulting in impaired sucrose excretion.