Various sonography studies have evaluated the normal flexor tendons of the fingers by reporting the echogenicity of these structures. Due to the descriptive nature of these studies, little information is available concerning the reproducibility of sonographic measures of the finger flexor tendons. The aim of this study was to determine whether sonography measurement of finger flexor tendons can provide reproducible information. The study used a test-retest, same-subject experimental design. Individuals who had no history of injury or surgery to the fingers had the right and left middle fingers of both hands assessed on two different occasions (test 1 and test 2) separated by at least 4 hours. The flexor tendons were assessed for continuity and measured for thickness at three points along the finger: the heads of the metacarpal, proximal phalanx, and middle phalanx. Reliability was assessed using Pearson's Correlation Coefficient ( r), t test (paired two-tail), and the intraclass correlation coefficient (ICC_1,1). The majority of measures had an excellent linear correlation ( r > 0.75). The t tests indicated that there were no significant differences between the two tests ( P [.lessequal] .05). High ICC_1,1 values suggested that there were excellent relationships between the measures on the two occasions of testing. No significant differences were found between measures of the left and right hands. The synovial sheath-pulley systems were evident as an echogenic specular reflection situated anteriorly to the flexor tendons in all individuals. Using this measurement protocol, sonography was found to be a reliable method of measuring and assessing the flexor tendons of the fingers.