Our experimental project to study&Lgr;Ninteraction using high-resolution hypernuclear &ggr; spectroscopy is described. Employing a germanium detector array (Hyperball), we investigated level structure of&Lgr;7Liand&Lgr;9Bein high precision and obtained quantitative information on the strengths of the spin-spin force and the &Lgr;-spin-dependent spin-orbit force between &Lgr; andN. More experiments are in progress to investigate the tensor force and the nucleon-spin-dependent spin-orbit force. ©2001 American Institute of Physics.