The 3100 dwt tanker Brothers 11 collided with the 3345 dwt tanker Valeriy Kalachev on the river Don near Azov, Russia.  The Brothers 11 was heading down river passing the Valeriy Kalachev which was going up the river.   The Brothers 11 had the right of way, but the Kalachev did not alter course when they struck.   The Brothers 11 suffered a three foot hole above the waterline while the Kalachev had a six foot hole in the bow near the anchor winch.   No one was injured on either vessel and no pollution was released.   Both vessels proceeded to Azov under their own power for survey and inspection.   Authorities are conducting an investigation into the incident.