During the outbreak, from 16 January 2002 to 3 March 2002, nasopharyngeal secretions obtained from 35 pediatric patients under 2 years of age and suffering from acute respiratory disease were tested by VIDAS respiratory syncytial virus (RSV) assay (an automated enzyme-linked fluorescent immunoassay) and reverse transcription- polymerase chain reaction (RT-PCR). RSV antigen was detected in 16 specimens by VIDAS RSV assay, and 15 of these were confirmed by the RT-PCR. A total of 18 samples were found to be positive by RT-PCR. RSV subgroup B was identified by further restriction fragment length polymorphism analysis using AvaII and BglII endonucleases in 17 of 18 (94%) RT-PCR positive samples. These findings indicated that RSV subgroup B was highly dominant during an outbreak of RSV infection among children in Ankara. To our knowledge, this is the first outbreak due to dominant RSV subgroup B documented in Turkey.