We present a phenomenological model for the dynamics of disordered (complex) systems. We postulate that the lifetimes of the many metastable states are distributed according to a broad, power law probability distribution. We show that aging occurs in this model when the average lifetime is infmite. A simple hypothesis leads to a new functional fornl for the relaxation which is in remarkable agreement with spin-glass experiments over nearly five decades in time. In spite of fifteen years of dispute, the theory of equilibrium spin-glasses is not yet settled (1, 2, 3). Dynamical effects are, however, likely to be the dominant aspect in experiments. One of the most striking aspects of the dynamics of spin-glasses in their low temperature phase is the aging phenomenon- a rather peculiar and awkward feature from the thermodynamics point of view : the relaxation of a system depends on its history. More precisely, if a system is field-cooled below its spin-glass temperature, the magnetization relaxation depends on the Waiting time t~ between the quench and the switch off of the magnetic field (4, 5, 6). Similar effects are observed on the viscoelastic properties of polymer melts (7), magnetic properties of HTC superconductors (8) and more recently on the relaxation after a heat pulse in Charge Density Wave systems (9). Analytical fits of the magnetization relaxation as a function of time have been proposed. In (6), it is proposed that the initial «stationary» part of the relaxation is a power-law With a small (negative) exponent. For times longer than the Waiting time, relaxation is Well fitted by a « stretched » exponential decay, provided that an effective time is introduced (6). In (4, 5), however, a stretched exponential of the «real» time was found for relatively short times. Many phenomenological theories have been devised to account for the stretched exponential decay lo-14), and for the slow part and aging (6, 15-18). We however feel that the basic mechanism underlying aging has not been fully appreciated (see however (17)) although it is, in our opinion, one of the constitutive properties of spin-glasses. The aim of this note is to suggest that aging is related to ergodicity breaking which has, in these systems, a peculiar and perhaps unexpected meaning. We find on some simple models that- according to our definition, see below « Weak » ergodicity breaking occurs in the spin-glass phase, defined as the phase Where the Edwards-Anderson parameter is non-zero. We see however no reason Why the two should be linked in general, and suggest that the appearance of aging could be