MARS14 Monte Carlo simulations were performed for collimation and shielding studies of the J‐PARC 3 GeV ring. A 400 MeV proton beam loss distribution, calculated with the STRUCT code, was used as a source term. The module locations in the ring and the curved tunnel sections were described by the MAD‐MARS beam line builder and a deep penetration calculation with good statistics was carried out using a 3‐dimensional multi‐layer technique. Prompt dose‐rate distributions were calculated inside and outside the concrete and soil shield, and an effective shielding design was made. The residual dose rates for various beam line materials were also calculated to estimate the external‐exposures during maintenance. In this paper, the calculation results are exemplified for the region from the injection through the collimator. © 2003 American Institute of Physics