Eighty-three beta-thalassemic patients, aged 1.5-19 years, were prospectively studied for evidence of gallbladder pathology by real-time, high-resolution ultrasound. Cholelithiasis was present in 7 patients (8.4%). Sludge, a clinical entity that, when it persists, can be a predisposing factor for cholelithiasis and cholecystitis, was detected in 29 patients (34.9%). Prevalence of sludge to this extent has not been reported in the literature and we believe this is due to better technology offered by modern ultrasound equipment. Pseudo-sludge, a condition that is created by a beam averaging effect (partial-volume phenomenon), at the diverging portion of the ultrasound beam, has always been confusing and a source of difficulties in the ultrasound examination of the gallbladder. For the first time, a method is described, to easily differentiate between true sludge and pseudo-sludge.