Shell-model calculations in a large model space are performed for the low-lying1/2+,3/2−and1/2−states in&Lgr;17O,introducing effective interactions among the &Lgr;, &Sgr; and nucleons. The effective interactions are derived from hyperon-nucleon and nucleon-nucleon interactions given in free space in the framework of the unitary-model-operator approach. The results are compared with those obtained in a perturbative method studied previously, and reliability of the present method is discussed. ©2001 American Institute of Physics.