Background & Objectives: There have been few studies on diadochokinetic performance in patients with hypokinetic dysarthria. In this study, differences in the rates and regularities of DDK tasks were compared between hypokinetic dysarthria patients and normal subjects. In addition, the differences between a mild and moderate form of the disorder were compared based on speech intelligibility. Methods: Eleven patients with mild hypokinetic dysarthria, seven with moderate hypokinetic dysarthria, and 26 normal controls were asked to perform DDK tasks. The subjects were asked to perform both AMR and SMR tasks which were acoustically analyzed using the Motor Speech Profile™(Model 4500) and the Praat computer program. Results: The hypokinetic dysarthria group demonstrated relatively slower rates of AMR compared to those of the normal group, while the rates of the SMR group were within the normal range. The hypokinetic group demonstrated irregular patterns in both AMR and SMR tasks compared to those of the normal group. In addition, hypokinetic dysarthria patients with different severities did not exhibit any differences in the rates of completion for the AMR and SMR tasks. However, the repetition of /p˄/ and /t˄/ in the AMR and the SMR tasks were more irregular in mild hypokinetic patients than they were in normal subjects, whereas the repetition of /k˄/ was more irregular in moderate hypokinetic patients than it was in the mild group. Discussion & Conclusion: The results of this study show the objective measurement of diadochokinetic performance in patients with hypokinetic dysarthria. Furthermore, these results made a significant contribution by analyzing the differences in diadochokinetic performance according to the severity of dysa