Some previous studies showed that Ureaplasma urealyticum is the most common germ that appears in the birthway of pregnant women and which is also frequently found in skin swabs and secretions of newborn and premature babies. The colonization of pregnant women by Ureaplasma urealyticum makes a premature birth more likely. Another factor of risk for a premature infant is a premature rupture of membranes for more than 24 hours which also makes an infection possible. There exists an association between pulmonary infection by Ureaplasma urealyticum and the development of a bronchopulmonary dysplasia especially for premature babies. According to our observations acute exacerbations of severe pneumonia can appear even after month. An attempt of therapy of pulmonary infection should be undertaken with erythromycin, if sensitive serotypes are present. In the case of erythromycin resistance chloramphenicol can be used but only under frequent controls of blood levels. We were able to observe rapid improvements with this effective therapy.