This research was performed to find out the phonological processes of the students with mental retardation as a function of intelligence and age. Forty-five students participated in this study. They were divided into 2 groups; one group for intelligence-the mild, the moderate, and the severe, the other group for age-12 to 13, 14 to 15, and 16 to 17.The articulation test containing 25 cards was administered.The frequency of phonological processes was calculated in percentage. An one-way ANOVA and Turkey's HSD test were performed. The results of this study were as follows:First, was as the intelligence lowered, the frequency of phonological processes became higher. The phonological processes showing the significant differences were alveolar omission, and alveolar backing, between the mild and the moderate group, palatal fronting, palatal backing, stop assimilation, and unaspiration, between the moderate and the severe group, and prevocalic omission, postvocalic omission, additions, stop omission, fricative omission, nasal omission, liquid omission, alveolar omission, velar omission, palatal fronting, velar fronting, alveolar backing palatal backing, labialization, alveolization, palatalization, stopping, affrication, nasalization, alveolar assimilation, velar assimilation, stop assimilation, tense assimilation, tensing, laxing, aspiration, and unaspiration, between the mild and the severe group. Second, a few differences were shown in the phonological processes for each age group. The phonological processes showing the significant differences were postvacalic omission, stop omission, labial omission, and velar omission, between 12-13 and 14-15 age group, syllable reduction, between 14-15 and 16-17 age group, and syllable reduction, labial omission, and alveolar fronting, between 12-13 and 16-17 age group.