<h3>Background</h3> The MSKUS has shown higher sensitivity in detecting synovitis than clinical examination in RA patients. However this imaging modality is considered as examiner – dependent.Since 2004 OMERACT ultrasound task force has standardized the acquisition and interpretation of US images including a scoring system for synovitis. <h3>Objectives</h3> To assess the intra- and inter-observer reliability of ultrasound (US) in scoring B-mode, Doppler synovitis and combined B-mode and Doppler synovitis in different peripheral joints of RA patients. <h3>Methods</h3> Four rheumatologists, who had received a formal MSKUS postgraduate training program with particular focus on definitions and scoring synovitis on B-mode and Doppler mode, participated in a patient-based reliability exercise. Sixteen active RA patients (ACR criteria 1987) were studied (14 female/2 male)/(DAS 28&gt;3.2), mean age 46.4±14.8 years, mean disease duration 9.8±4.2 years. The rheumatologists group independently and consecutively performed a B-mode and power Doppler (PD) US assessment of 7 joints (i.e. elbow, radiocarpal, midcarpal, knee, ankle, and second and third metacarpophalangeal joints) of each patient in two rounds in a blinded fashion. Each joint was semiquantitatively scored from 0 to 3 for B-mode synovitis (BS), Doppler synovitis (DS), and combined B-mode/Doppler synovitis (CS).The US assessment was performed using four commercially available real-time scanners (i.e. two MyLab Class C, one MyLab alpha, one MyLab one; Esaote, Genoa, Italy) equipped with multifrequency linear transducers (6-13 MHz). Intra-observer reliability was assessed by Cohen9s κ. Inter-observer reliability was assessed by unweight Light9s κ. <h3>Results</h3> The main prevalence on synovitis on B-mode was 83%,the distribution of the assigned scores were the following: grade 1 in 18%, grade 2 in 32%,grade 3 in 33%.In 55% of joint synovial PD signal was detected and the distribution of scores was 15% of joint for grade 1,26% for grade 2, and 14% for grade 3. In general the intra-observer and inter-observer reliability for BS, DS, and CS in all joints and each joint was good to excellent (κ values 0.6-1). <h3>Conclusions</h3> Formal,structured and continuous training in musculoskeletal ultrasound brought a good to excellent reproducibility.We have also been able to show that a MKUS has a high reliability in real - time acquisition BS,DS and CS modalities for scoring synovitis in patients with active rheumatoid arthritis. <h3>References</h3> Naredo E, Rodriguez M, Campos C, et al. Validity, reproducibility,and responsiveness of twelve-joint simplified power doppler ultrasonographic assessment of joint inflammation in rheumatoid arthritis. Arthritis Rheum 2008;59:515-522. <h3>Acknowledgements</h3> Clinica las Americas, Pasto, Colombia. AbbVie. Universidad de la Sabana, Bogota, Colombia. Asociacion Colombiana de Reumatologia. <h3>Disclosure of Interest</h3> None declared