  The ARGO-YBJ experiment will be installed at YangBaJing Cosmic Ray Laboratory (Tibet, P.R. China), 4300 m a.s.l. . It consists of a full coverage of about 10^4 m^2 realized with RPC chambers.   A small carpet of about 50 m^2 has been operated at YangBaJing in order to check the RPC performance in these high altitude conditions.   Results concerning efficiency and time resolution are reported. 
Performance of RPCs operated at the YangBaJing Laboratory