Objective: The purpose of the study was to investigate the effects of flow phonation voice therapy on laryngeal physiology and vocal quality in persons with primary Muscle Tension Dysphonia (MTD1). Method(s): Seventeen participants with a diagnosis of MTD1 completed the study. Participants were randomized to two groups. Group 1 (9 participants) received flow phonation treatment and individualized vocal hygiene education for 12 sessions over six weeks. Group 2 (8 participants) received vocal hygiene education only for three weeks (6 sessions), followed by another three weeks (6 sessions) of both vocal hygiene instruction and flow phonation therapy. Treatment consisted of cup-bubble blowing, gargling, and stretch and flow exercises. Visual-perceptual. auditory-perceptual, acoustic, aerodynamic and voice-related quality-of-life measures were obtained at three time points: before treatment, three weeks after initiation of treatment and after completion of treatment. Result(s): Voice quality was perceived to be significantly improved in both groups. Voice related quality-of-life trended toward improvement for both groups across time points. Changes in aerodynamic and acoustic measures did not reach statistical significance compared to baseline for both groups. Visual comparisons of laryngeal closure patterns demonstrated comparably better outcomes for Group 1. Conclusion(s): Results of this study indicate flow phonation exercises can potentially be favorably employed for individuals with MTD1. In particular, it appears that the exercises aid in alleviating vocal hyperfunction, as evidenced by visual perceptual stroboscopic analysis, and clinically improved auditory-perceptual measures.