RSV A2 induces more cytopathic effects (CPE) than the 3 clinical isolates. PBECs from 5 individual donors were infected with RSV A2, BT2a, BT3a and BT4a (MOI of 0.1) during 2 h and washed with PBS. Seventy two hpi, cells were examined by phase contrast microscopy. Micrographs of a representative field for each RSV strain are presented. PBECs infected with RSV A2 demonstrated substantial CPE, whereas cells infected with RSV BT2a and BT3a displayed only limited CPE. Cells infected with RSV BT4a did not demonstrate any obvious CPE and were similar to non-infected cultures. Original magnification, x10.