To meet urgent requirements for data validation, an experimental analysis has been carried out for isotopic radioactivity induced by deuterium-tritium neutron irradiation in structural materials. The primary objective is to examine the adequacy of the activation cross sections implemented in the current activation calculation codes considered for use in fusion reactor nuclear design. Four activation cross-section libraries, namely, JENDL, LIB90, REAC*63, and REAC*175 were investigated in this current analysis. The isotopic induced radioactivity calculations using these four libraries are compared with experimental values obtained in the Japan Atomic Energy Research Institute/U.S. Department of Energy collaborative program on fusion blanket neutronics. The nine materials studied are aluminum, silicon, titanium, vanadium, chromium, MnCu alloy, iron, nickel, niobium, and Type 316 stainless steel. The adequacy of the cross sections is investigated through the calculation to experiment analysis. As a result, most of the discrepancies in the calculations from experiments can be explained by inadequate activation cross sections. In addition, uncertainties due to neutron energy groups and neutron transport calculation are considered. The JENDL library gives the best agreement with experiments, followed by REAC*175, LIB90, and REAC*63, in this order. Clear suggestions for a future direction to improve the overall calculation accuracy are developed based on the current experimental analysis.