The major consonant assimilation processes occurring in Classical and Colloquial Arabic are listed (classified as progressive or regressive, partial or complete), and an autosegmental analysis is performed on them. It is argued, on the basis of the autosegmental approach to the underlying representation of segments and to the application of phonological rules adopted in this paper, that partial and complete assimilation rules are just two forms of the same process since they apply in the same manner. Both types of assimilation involve the transfer of one or more features of a certain segment onto an adjacent one so that the latter becomes partially or totally like the former. The only difference between the assimilation types is found in their outcome, but this difference is not found to have any bearing on the behavior of the output of assimilation toward phonological rules like epenthesis. The analysis is then shown to be in harmony with the Obligatory Contour Principle concerning the phonological status of the geminate consonant clusters resulting from the phonological rules of assimilation. (MSE)