Diacerein (DR) is widely used to treat osteoarthritis (OA) and belongs to a group of symptomatic slow-acting drugs for OA (SYSADOA). One of the major benefits of this drug is a low risk of serious adverse events(AE). However,Russiahas not conducted its own large-scale trials of the safety of DR despite its popularity. Objective: to estimate the frequency of AE of DR (Diaflex®, Romfarm) in real clinical practice. Subject s and methods. The use of DR was retrospectively analyzed in 3479 patients (60.4% women and 39.6% men; mean age 57.6±12.6 years) with OA and back pain. DR was used in a dose of 100 mg/day; treatment results were assessed following 30 days. The patients received combination therapy: in addition to DR, 62.6% took nonsteroidal anti-inflammatory drugs, as well as myorelaxants, local glucocorticoid injections, other SYSADOA, etc. The efficiency of therapy (visual analogue scale (VAS) pain changes and treatment satisfaction), and the frequency and nature of AE were assessed. Results. Combination therapy using DR was effective in the majority of patients: VAS pain intensity decreased from 71.2±17.5 to 22.6±16.3 mm; 76% of the patients rated their treatment results as good or excellent. Major AE involved the gastrointestinal tract; obvious gastralgia, nausea, and a sensation of heaviness were observed in only 1.7, 1.8, and 2.4% of the patients, respectively. There were frequent stools: 5.91±1.9 defecation episodes per week at baseline; 7.3±2.8 episodes per week after 30 days of DR administration (p < 0.001). Only 30 (0.86%) patients developed marked diarrhea. There was a considerable (more than two-fold higher than the upper reference limits) increase in alanine aminotransferase and aspartate aminotransferase (ALT/AST) levels in only 20 (0.57%) patients. Conclusion. Combination treatment using DR is effective in reducing pain in patients with OA and low back pain. DR is well tolerated and rarely causes serious AE. Marked diarrhea and significantly elevated ALT/AST levels are seen in less than 1% of the patients taking