             Seyhan Boyoglu, a Komal Vig a , Adam Pfendt b , Shreekumar Pillai a , Gerold A. Willing b , Shree R. Singh a , a Center for NanoBiotechnology Research, Alabama State University, Montgomery, AL, USA, b J.B. Speed School of Engineering, University of Louisville, Louisville, KY,USA  Respiratory Syncytial Virus (RSV) is one of the most common viral causes of upper and lower respiratory tract infections in infants and results in pneumonia. In the present study, we used AFM to observe the effect of Gold and Silver nanoparticles on RSV virus particles. The results indicated that RSV particles were almost round in shape as detected by AFM. Even though the dimensions of the RSV particle exhibited a polymorphous distribution via off1line particle analysis of AFM, most of the RSV particles had a diameter of approximate 135nm. When we mixed RSV with gold nanoparticles, we observed that gold nanoparticles were bound around RSV and RSV started shrinking in size. Further,   infection of Hep12 cells were performed with either RSV alone or RSV mixed with gold nanoparticles. Infected cells were fixed at different time intervals to observe RSV entry into the cells and propagation of the infection.  RSV AFM, gold, silver. Nanoparticles  !"#$!" Respiratory Syncytial Virus is the leading cause of severe respiratory illnesses such as bronchiolitis and pneumonia in young children. RSV is a  with negative1sense genomic RNA that encodes for eleven proteins, two of which, F and G are major surface proteins. The G protein is responsible for viral attachment to the host cell, while the F protein facilitates viral entry and spread of the virus from infected to normal cells leading to syncytia formation. Nanoparticles have been gaining extensive usage in medicine and therapy. The structural characteristics of metal nanoparticles and their interactions with surface modifiers are essential to their functions, 1 as they should be stable enough to work with at ambient conditions. In the present study, we synthesized and used silver and gold nanoparticles to study the inhibition of RSV using Atomic Force Microscopy (AFM). AFM images provide a tool to elucidate the topography of viral and cell surface interactions. Based on the interactions of these structures and their images we can get a better understanding on how the fusion occurs. Since many medically important virus proteins HIV11 gp41, influenza HA, and coronovirus peplomer, share similar structure and functions, this study may prove valuable to design therapeutic agents and vaccines against these viruses. % !& ’ ("# %)   PVP coated silver nanoparticles were synthesized using a sonochemical method. The experimental procedure for a typical reaction is as follows: 1g of silver(I) acetate (Sigma Aldrich 98+%) was mixed in 60ml of DMF (Dimethylformamide) and this reaction mixture was irradiated with a high1intensity ultrasonic horn (Ti1 horn, 20 kHz, 100 W/cm2) under argon at room temperature for 3 h. The product obtained was washed thoroughly with absolute ethanol several times and dried under vacuum for overnight. %)%   Gold nanoparticle colloidal solution was also bought commercially from Nanoparts TM Inc. with a concentration of 1.51 x 10e + 11 particles/ml. NSTI-Nanotech 2009, www.nsti.org, ISBN 978-1-4398-1783-4 Vol. 2, 2009 146