During the 17th century and mainly in the 18th century, medical care in the Czech lands dramatically changed. It was closely connected with the arrival of the Brothers of Charity in the beginning of the 17th century at first to Valtice (1605) and shortly after to Prague (1620). They founded the hospital for men in the Old Town in Prague (at the place of medieval hospital of Bohuslav). A hospital specialized for care of women patients was founded in Prague hundred years later, in 1719, by 'Alzbetinky' (Catholic religious order of St. Elisabeth), in the Prague New Town in the Na Slupi Street. The mission of both houses was not the charity and care of the poor and infirm people any more, but ill people (mainly those from lower social classes) were professionally treated by trained staff there. The books listing accepted patients have been preserved in the archival records of both medical houses. They are very important because of the information about morbidity and mortality of the Prague population since the 17th (and the 18th - in case of 'Alzbetinky') centuries, about patients' age, and, to a certain extent, they make some social aspects clear. However, above all, recorded diagnoses bring information about the level of medical knowledge of those days and about the development of new pieces of knowledge. Single illnesses, because of which patients were taken to hospital, were not diagnosed exactly. Mainly, instead of a 'name' of the illnesses or a cause of death only the place of sickness or accident were given and symptoms were described - but those descriptions were the same for more illnesses. One illness could be named in more different ways, on the other hand names for some sickness did not need to be (and mostly were not) precise because of the low level of diagnostics. We can find among the most mentioned illnesses mainly not specified fibre, sicknesses of digestive organs, respiratory and circulation organs. Infectious illnesses were very spread, caused mainly by poor hygienic conditions of lower social classes. Unusual events can be studied in the books of patients as well - especially epidemics and wars. The number of patients changed (it was quite low in the period of plague because of hygienic measures, and it increased in the war times) and the type of illnesses, too.