Over the last 10 years, the assimilation process referred to as vowel harmony has served as a test case for a number of proposals in phonological theory. Current autosegmental approaches successfully capture the intuition that vowel harmony is a dynamic process involving the interaction of a sequence of vowels; still, no theoretical analysis has offered a non-stipulative account of the inconsistent behavior of the so-called ‘transparent’, or disharmonic, segments. This paper proposes a connectionist processing account of the vowel harmony phenomenon, using data from Hungarian. The strength of this account is that it demonstrates that the same general principle of assimilation which underlies the behavior of the 'harmonic' forms accounts as well for the apparently exceptional "transparent' cases, without stipulation. The account proceeds in three steps. After presenting the data and current theoretical analyses, the paper describes the model of sequential processing introduced by Jordan (1986), and motivates this as a model of assimilation processes in phonology. The paper then presents the results of a series of parametric studies that were run with this model, using arbitrary bit patterns as stimuli. These results establish certain conditions on assimilation in a network of this type. Finally, these findings are related to the Hungarian data, where the same conditions are shown to predict the correct pattern of behavior for both harmonic and transparent vowels.