Electronic Journal of Differential Equations, Vol. 2012 (2012), No. 73, pp. 1-14. Title: Decay results for viscoelastic diffusion equations in absence of instantaneous elasticity Author: Mohammad Kafini (KFUPM, Dhahran, Saudi Arabia) Abstract: We study the diffusion equation in the absence of instantaneous elasticity $$ u_t-\int_0^{t}g(t-\tau )\Delta u(\tau )\,d\tau =0,\quad (x,t)\in \Omega \times (0,+\infty ), $$ where $\Omega \subset \mathbb{R}^n$, subjected to nonlinear boundary conditions. We prove that if the relaxation function g decays exponentially, then the solutions is exponential stable. Submitted December 18, 2011. Published May 10, 2012. Math Subject Classifications: 35B05, 35L05, 35L15, 35L70. Key Words: Diffusion equation; instantaneous elasticity; exponential decay; relaxation function; viscoelastic.