Kojima Productions is currently only comprised of four employees, according to a report from The New Yorker.
The members of staff include director/game designer Hideo Kojima, art director Yoji Shinkawa, and Kenichiro Imaizumi, a former producer at Konami. The identity of the fourth employee isn't yet clear. [UPDATE: It appears to be Kojima's personal assistant Ayako Terashima. Thanks, Johnny.]
The studio is currently hiring for many more members of staff, however, including programmers, artists, designers and a composer. The full list of openings can be found on the developer's website.
Kojima opened Kojima Productions on Wednesday after his contract with Konami was "terminated".
Source: newyorker.com, kojimaproductions.jp