Ultrasonography was used to measure flexor tendon sheath thickness in 14 insulin-dependent (IDDM) diabetics with diabetic cheiroarthropathy (DCA) and compared to 17 IDDM patients without DCA along with 10 healthy volunteers. Assessment was also made of the presence of systemic diabetic microvascular disease complications. A blinded visual 'eyeball' report on the ultrasound scans by a radiologist found hypoechoic thickening of the flexor tendon sheaths in 12 of the 14 patients with DCA, three of the 17 unaffected diabetics and two of the healthy volunteers (Fisher's exact, P < 0.001). However, further quantitation of tendon sheath thickness separated patients with DCA from others. In all patients with DCA, tendon sheath thickness was > or = 1 mm (median 1.8 mm, range 1.0-2.3 mm) and < or = 1 mm in the other two groups (medians 0.6 and 0.5 mm, range 0.3-1.0 mm) (Kruskal-Wallis, P < 0.001). All patients with DCA had evidence of systemic microvascular disease complications, particularly proliferative retinopathy (82%). It appears that flexor tendon sheath thickening in the hand is an integral part of the pathology in DCA and is easily demonstrated by ultrasound. It is closely associated with overt diabetic microvascular disease complications.