This paper presents a model for the rheology of soft glassy materials, such as foams, emulsions, and slurries. The authors argue that the common rheological behavior of these materials is due to shared structural disorder and metastability. A generic model is introduced, where interactions are represented by a mean-field noise temperature x. The model predicts power law fluid behavior with or without a yield stress, depending on the value of x. For 1 < x < 2, both storage and loss moduli vary with frequency as ω^{x-1}, becoming flat near a glass transition (x = 1). Values of x ≈ 1 may result from marginal dynamics, as seen in some spin glass models. The model is tested by considering the behavior of a foam or dense emulsion under shear. The system is sheared, causing droplets to deform elastically and then rearrange to new positions, relaxing stress. The mesoscopic strain l executes a saw-tooth motion as the macroscopic strain γ is increased. The local shear stress is given by kl, with k an elastic constant. The yield point defines a maximal elastic energy E = ½kl_y². The authors model the effects of structural disorder by assuming a distribution of yield energies E, rather than a single value. The state of a macroscopic sample is characterized by a probability distribution P(l, E; t). The dynamics of P are described by a partial differential equation, which includes terms for elastic deformation, yielding, and relaxation. The model predicts that for x > 1, the system evolves towards the Boltzmann distribution, while for x < x_g, no equilibrium state exists, and the system shows weak ergodicity breaking and aging phenomena. For x < 1, the system shows a yield stress. The model is tested against experimental data, showing good agreement with the observed behavior of soft materials. The authors also discuss the origin and magnitude of the "attempt frequency" Γ₀ and the "noise temperature" x. They argue that x values close to unity may be normal, as seen in some spin glass models. The model is also tested against steady shear flow experiments, showing good agreement with the observed behavior of soft materials. The authors conclude that the model provides a good description of the rheology of soft glassy materials, and that the common behavior of these materials is due to shared structural disorder and metastability.This paper presents a model for the rheology of soft glassy materials, such as foams, emulsions, and slurries. The authors argue that the common rheological behavior of these materials is due to shared structural disorder and metastability. A generic model is introduced, where interactions are represented by a mean-field noise temperature x. The model predicts power law fluid behavior with or without a yield stress, depending on the value of x. For 1 < x < 2, both storage and loss moduli vary with frequency as ω^{x-1}, becoming flat near a glass transition (x = 1). Values of x ≈ 1 may result from marginal dynamics, as seen in some spin glass models. The model is tested by considering the behavior of a foam or dense emulsion under shear. The system is sheared, causing droplets to deform elastically and then rearrange to new positions, relaxing stress. The mesoscopic strain l executes a saw-tooth motion as the macroscopic strain γ is increased. The local shear stress is given by kl, with k an elastic constant. The yield point defines a maximal elastic energy E = ½kl_y². The authors model the effects of structural disorder by assuming a distribution of yield energies E, rather than a single value. The state of a macroscopic sample is characterized by a probability distribution P(l, E; t). The dynamics of P are described by a partial differential equation, which includes terms for elastic deformation, yielding, and relaxation. The model predicts that for x > 1, the system evolves towards the Boltzmann distribution, while for x < x_g, no equilibrium state exists, and the system shows weak ergodicity breaking and aging phenomena. For x < 1, the system shows a yield stress. The model is tested against experimental data, showing good agreement with the observed behavior of soft materials. The authors also discuss the origin and magnitude of the "attempt frequency" Γ₀ and the "noise temperature" x. They argue that x values close to unity may be normal, as seen in some spin glass models. The model is also tested against steady shear flow experiments, showing good agreement with the observed behavior of soft materials. The authors conclude that the model provides a good description of the rheology of soft glassy materials, and that the common behavior of these materials is due to shared structural disorder and metastability.