In rheumatological practice, the differential diagnosis of subcutaneous nodules includes mainly rheumatoid nodules, gouty tophi and, exceptionally, the tophus of cholesterol [1] as well as the tophus in calcium pyrophosphate dihydrate (CPPD) crystal deposition disease [2]. The purpose of this study, involving two cases of chronic tophaceous gout, is to assess the usefulness of computed tomography (CT) imaging of subcutaneous tophi. Indeed, we have previously demonstrated that CT can reveal, within the knee joints of patients with gout, the presence of opacities that were considered to be MSU deposits [3]. We have previously measured the density of 20 opacities in nine knee joints: the mean ( • 2SD) value was 170 _+ 30 Hounsfield units (HU), which was in the same range as that of tophi in vitro [3]. tender; subcutaneous tophi were found bilaterally over the olecranon processes and Achilles tendons and on the right little finger (Fig. la). The skin above the tophi was of normal colour and was not ulcerated. Plain radiographs failed to reveal bony erosions or opacities within the nodules of the hand. Helical CT imaging was performed with a GE scanner (9800 high-speed advantage) using 120 kV, 140 mA and 1 mm collimation (table speed 1 mm/s, pitch 1). Round and oval opacities were seen, measuring 2-6 mm in diameter (Fig. lb); the mean ( + 2SD) density of these opacities was 165 _+ 40 HU, i.e. in the same range as that found in the knee joints [3]. Histological examination of the tophus, which was surgically resected, showed birefringent MSU crystal deposits embedded in fibrous tissues (Fig. lc), whose diameter was 2-5 ram.