We discuss the possibility that the stellar system Cyg OB2 No.5 can be a ga
mma-ray source in the light of recent EGRET and radio data. This system is
formed by an O7 Ia + Ofpc/WN9 contact binary. A third star, probably a B0 V
star also associated with the system, is located at similar to 1700 AU fro
m the primary. We estimate the expected gamma-ray luminosity from the colli
ding winds region, the terminal shock of the wind, and the unstable zone at
the base of the wind, and conclude that, undervery reasonable assumptions,
Cyg OB2 No.5 can generate about a half of the gamma-ray flux detected from
the positionally coincident source 3EG J2033+4118. We suggest, then, that
other O stars belonging to the association, also placed within the 95% prob
ability EGRET location contour, could contribute to the observed gamma-ray
flux.