A registry for chronic radiation syndrome (CRS), a deterministic effect of chronic exposure to external and/or internal radiation at doses and dose rates exceeding thresholds for tissue reactions, was established within a medical and dosimetry database known as 'Clinics', of the Southern Urals Biophysics Institute at the Federal Medical and Biological Agency of Russia. It includes 2068 CRS cases: 1517 (73.4%) in males and 551 (26.6%) in females. The majority of workers (97.9%) diagnosed with CRS at one of the main facilities of the first Russian nuclear enterprise, Mayak Production Association, were hired in the period 1948-1954. On the date of CRS diagnosis, the mean cumulative red bone marrow (RBM) absorbed doses from external gamma rays were 1.1 ± 0.66 Gy in males and 1.0 ± 0.58 Gy (±standard deviation) in females, with mean annual doses of 0.46 ± 0.33 Gy and 0.38 ± 0.22 Gy, respectively, and maximum annual doses of 0.67 ± 0.46 Gy and 0.55 ± 0.34 Gy, respectively. The frequency of CRS cases significantly increased with the increasing cumulative and mean annual RBM absorbed doses from external gamma rays. The paper presents the structure and descriptive characteristics of the CRS registry as well as prospects for its use.