This work gives the total dose and the spectral distribution at any specific point inside a tissue equivalent cylindrical phantom due to Pu-Be neutron source. The absorbed dose through the material are coming from 17 reactions between the neutrons and the phantom constituents: H 2 ,0 2 ,N 2 . and C. The changes in the neutron spectra are due to energy loss as a result of neutron slowing down. A computer program is used to carry out these calculations using the Monte-Carlo technique.