We applied the FT to glassy systems. It has been claimed in the past that as the glass transition is approached both the Fluctuation Dissipation Theorem (due to Einstein) and the Evans–Searles Fluctuation Theorem (ESFT) break down. We have shown that these claims are false. Using a combination of theory and computer simulations we have shown that the Fluctuation Dissipation Theorem (FDT) does not fail, but rather as the glass transition is approached the range of field strengths over which linear response can be expected shrinks to zero. Inside the linear response domain the FDT always works. Outside this domain the FDT does not apply. The previous claims that the ESFT fails as the glass transition is approached, are simply due to sampling problems as the glass transition is approached. When sampling is carried out with sufficient care, the ESFT always works – as expected from theory.