The invention relates to a method for detection of ligands (agonists or antagonists) specific to a receptor (RCPG) coupled to a G protein, comprising the following steps; 1) bring a receptor marked with a member of a donor/acceptor pair into contact with a G.alpha. or Gss sub-unit of a G protein marked with the other member of the donor/acceptor pair and 2) measure the transfer by proximity effect between the donor and acceptor.