The Ukrainian resort town of Yalta is hosting an informal summit of CIS countries.
Russian President Dmitry Medvedev is there alongside the leaders of Belarus, Kazakhstan, Azerbaijan and Armenia.
The gathering was organized by Ukrainian President Viktor Yanukovich, who will also take the opportunity to celebrate his 60th birthday with close allies.
Since Yanukovich took office in February, Ukraine's relations with the CIS countries, and Russia in particular, have been steadily improving.
When the talk turns to business, it is expected the leaders will discuss closer economic links.