Here we report the spread of respiratory syncytial virus (RSV) infection among three patients, who were hospitalized in an adult hematopoetic stem cell transplantation (HSCT) unit because of hematologic diseases, and effects of RSV infection on post-transplant outcome. The patients were placed into reverse isolation for administration of preparative regimens (high dose chemotherapy) in HSCT unit with high-energy particulate air (HEPA)-filtered single rooms. First case was a 62 years-old man with advanced multiple myeloma, which was refractory to multiple line treatment with high dose steroid including regimens and with secondary acute myelogenous leukaemia (AML); second case was a 45 years-old male patient with multiple myeloma, who had undergone autologous HSCT following high dose chemotherapy; third case was a 52 years-old man with AML that was refractory to multiple line treatment and had undergone allogeneic HSCT from a HLA-matched unrelated donor. Nasopharyngeal aspirate samples were collected from the patients in order to search for RSV positivity. RSV was investigated by in-house nested polymerase chain reaction (PCR) in the first patient and by direct antigen detection method (Monofluoscreen RSV-Biorad, France) in the others. First case had clinical picture of RSV infection just on the HSCT day when high dose chemotherapy has already been given. As RSV-RNA analysis yielded positive result, peroral ribavirin was initiated. Engraftment did not occur in this patient. He developed severe respiratory failure which necessitated mechanical ventilatory support, however, he has succumbed. After the detection of RSV positive index case, weekly screening of RSV in other five patients in the same unit had been performed. Following the first case, after nine and 17 days, respectively, RSV positivity was detected in two more patients. While clinical signs and symptoms of RSV infection developed in second case, third case remained asymptomatic. Both of the following patients had received ribavirin very early at first RSV positivity and recovered from RSV infection. Engraftment did not occur in the last patient who had undergone allogeneic HSCT from a HLA-matched unrelated donor and a second HSCT was performed. As a result, in HSCT patients, early diagnosis of RSV infection by PCR analysis may provide support to postpone immunosupressive treatment and help assesment of the management.