A method is given for calculating the heavy ion subbarrier fusion cross section for nuclei which are described by the interacting boson model. Explicit formulas are given for the case when the target is rotational, including both quadrupole and hexadecapole couplings. Calculations of the fusion cross section, average angular momentum, and distribution of barriers for {sup 16}O+{sup 154}Sm are compared with experimental results and with predictions of the geometrical model.