The physical behavior of integral data in an infinite medium has been evaluated for incident fusion neutrons with the help of the 3-D Monte Carlo Code. In a fusion reactor blanket with finite dimension, the integral quantities will be more or less different from the infinite medium results, depending on the neutron leakage fraction. Design studies foresee reduction of the neutron leakage out of the blanket to very low levels in order to prevent nuclear heating in superconducting fusion magnets and to keep all neutrons primarily in the coolant. The most important materials in fusion technology, namely tritium, beryllium, lead, and uranium have been investigated in an infinitive medium. The main purpose of this work is to calculate integral neutronic data for incident 14.1-MeV (D,T) fusion source neutrons in an infinite medium for the most important materials in fusion technology, namely lithium, beryllium, lead and uranium. The study concludes the calculation of the integral tritium breeding ratio, Pu-239 breeding rate, neutron multiplication ratio through (n, x) and fission reactions and that of the heat release in those mixtures that are composed, first when natural uranium and U-238, are mixed with natural lithium or Li-6 for a volume fraction from 0% to 100%, and then, the variable uranium-lithium composition is mixed with Be or Pb for a volume fraction from 0% to 100%. (C) 2003 Elsevier Ltd. All rights reserved.