Abstract Background: Ceftriaxone is known to induce reversible precipitations, called billiary sludge or pseudolithiasis in the gall bladder. Objective: The aim of this study was to investigate the frequency of biliary sludge and factors that contribute to this side effect in children. Methodology: This study was conducted on 50 consecutive children who were admitted at paediatric department of Bangabandhu Sheikh Mujib Medical University (BSMMU) for different illness and who received ceftriaxone in different dosage and duration. Ultraso-nography of hepatobiliary system was done before and at the end of therapy. Children who developed biliary sludge, a third ultrasonography was done after one month.