Ultrasound-induced cavitation has been extensively used to enhance the efficiency of nonviral-based gene delivery. Although such unique mechanical force could possibly augment the efficacy of retrovirus-mediated gene transfer, we harnessed an alternative approach, a resonant acoustic field, to facilitate the retroviral transduction rate. NIH 3T3 fibroblast cells suspended in a culture well and mixed with ecotropic retroviruses were co-treated with megahertz resonant acoustic fields (RAF). Suspended NIH 3T3 cells under RAF treatment agglomerated at acoustic nodal planes by primary radiation force within a short exposure time. These first arrived and agglomerated cells formed bands as nucleating sites for nanometer-sized ecotropic retroviruses circulated between nodal planes to attach on and thereby increased cell-virus encounters. According to the neomycin-resistant colony assay, 2-fold increment of retroviral transduction rate was obtained by exposing cells and retroviruses in the RAF for 6 min in the presence of 8 mu g/mL Polybrene.