The dual-jet slot die is the most common device used for producing melt-blown fibers. In this die, high-velocity air impinges upon a polymer stream. A comprehensive model was applied to predict the performance of these slot dies. This model involves the simultaneous solution of the momentum, energy, and continuity equations that are applied to the fiber threadline. Predicted parameters include fiber attenuation, vibration frequency, vibration amplitude, temperature, and stress. Experimental measurements were taken during melt blowing with an actual slot die. These measurements compared very well with the simulated results.