A group of 55 hematological patients treated for the last 2.5 years by the method of selective decontamination was evaluated. Though both institutes (Bad Saarow, Hradec Králové) worked on the problem in the same conditions (indications for the treatment, characteristics of patients, basic drugs), many differences in details were found. However, the important clinical results were the same: A statistically significant decrease in infections and duration of fever in treated patients. A survey of therapy complications, surveillance of infections and incidence of microbes are presented. The evaluation showed that future research including microbiological and immunological investigation based on a standard protocol will be useful.