PURPOSE: to evaluate and compare the fluency between the familial and the sporadic persistent developmental stuttering, characterizing the typology and the frequency of the disfluencies, the speech rate and the severity of the stuttering. METHOD: 40 participants aged from 6 to 42 years old, divided in two groups with twenty participants in each one: Familial Persistent Developmental Stuttering and Sporadic Persistent Developmental Stuttering. The procedures used were: clinical and familial history, assessment of fluency and Stuttering Severity Instrument. RESULTS: there were no statistically significant differences between the groups regarding the frequency of stuttering like disfluencies, the flow of syllables and words per minute and the severity of stuttering. It was noted a tendency of the group with familial stuttering to show a bigger variability of the severity of stuttering, going from mild to very severe, whereas in the group with sporadic stuttering, the severity varied from mild to severe. CONCLUSION: this study represents the first effort to the characterization of the speech fluency profile of the subgroups of people who stutter, namely familial persistent developmental stuttering and sporadic persistent developmental stuttering. It is possible to conclude that the speech fluency profile of people who stutter, independently of the familial history, is similar. It is noteworthy that the occurrence of some stuttering-like disfluencies, monosyllabic word repetition, block and intrusion were different between groups.