To investigate the neutron dose and spectra around a fast reactor from the point of view of radiation protection and shielding, neutron measurements were conducted at the reactor top of JOYO, a Japanese experimental fast reactor, and an analysis by a transport calculation was performed. The measurements were carried out under a Mark II irradiation core with and without the reactor top concrete pit cover at 98- and 48-MW(thermal) power levels, respectively. The measurements were performed at several points in and around the reactor top pit room. Neutron detectors with well-examined response functions were employed for this study—the rem (sievert) counter as a neutron dosimeter and the multimoderator neutron detector as a neutron spectrometer. The measured neutron doses distributed from 0.4 to 100 mrem/h·[100 MW(thermal)]−1 {4 to 1000 μSv/h· [100 MW(thermal)]−1 } and the measured neutron spectra showed an ∼1/E type energy distribution. The rapid spatial change of the neutron spectrum could not be observed near the reactor top. The neutron flux distributions around the reactor were calculated and compared with the measured results. The two-dimensional transport code DOT 3.5 was employed for the calculation, and the neutron group constants were prepared by using JENDL-2 cross-section libraries. The values of measurements and calculations were in relatively good agreement within a factor of 3 to 5 in spite of the 12-decade decrease in neutron flux from the reactor core center. It is shown that the effect of stored fuels in invessel storage racks has greatly affected the neutron dose rate at the reactor top. The modeling for shielding calculations of the iron rotating plug structures is discussed.