The aim of the research was to analyse the prevalence of ankylosing spondylitis (AS) in Poland and to assess the costs generated by AS patients in the system of public health care. The database of national payer-National Health Fund (NHF)-has been analysed. For the analysis, the information has been extracted from IT system about each treated patient with ICD-10 = M45 code as main or coexisting diagnosis included in the mandatory reports from entities of public healthcare service. In the years 2008-2013, from 28,800 to 32,800 persons diagnosed with AS as main or coexisting diagnosis have been registered in NHF database. In 2013, the prevalence amounted to 7.48 for 10,000 persons of general population-the highest in Kujawy-Pomerania province (10.92 per 10,000 inhabitants), Silesia (10.04) and Świętokrzyskie province (9.81). In male patients, this coefficient amounted to 8.91 per 10,000 inhabitants, whereas in female-to 6.15. In 2013, the prevalence for men was the highest in the age group of 60-64 years and for women in the group of 65-69 years. The healthcare expenses related to AS financed by the NHF increased from 13,200 million PLN (6.3 million USD) in 2008 to 72,600 million PLN (21,900 million USD) in 2013. The increase in healthcare expenses related to AS patients in the public healthcare system is significant and noticeable. High regional diversity is also a vital issue. It is necessary to carry out further research on the incidence rate of AS in Polish population.