Lecture article is devoted to the evolution of terminology and epidemiological aspects of bladder pain syndrome (BPS)/interstitial cystitis. The results of BPS prevalence studies vary widely due to the use of different diagnostic criteria for BPS and different research methodologies. The lowest values are demonstrated in studies in which the incidence of BPS was estimated by the number of already established diagnoses (from 4,5 to 158/100 000 women and from 1,2 to 63,5/100 000 in the general population) and significantly higher when questioning patients (265-1400/100 000 women) and when identifying symptoms characteristic of BPS during interviews (830-6500/100 000 women). The incidence of BPS in women is 5-9 times higher than in men. The highest incidence is observed in patients aged 40 to 59 years. In most patients diagnosed with BPS, bladder pain is combined with pain in other locations. A connection between BPS and irritable bowel syndrome, migraine, fibromyalgia, allergic reactions, and autoimmune diseases has been noted. Most patients with BPS have psycho-emotional and sexual disorders. Despite the significant number of publications devoted to the study of BPS epidemiology, comparison of their results is complicated by the lack of standardized research methods, the development of which seems to be a very urgent task for medicine.