BACKGROUND: Parkinson ś disease (PD) is characterized by small, slow movements affecting balance and gait. Lee-Silverman-Voice-Treatment-(LSVT)-BIG is an intensive intervention aiming to restore normal amplitudes of movements. This study aimed to examine whether LSVT-BIG influences dynamic balance and gait in persons with PD. METHODS: We used a Single-Subject-Experimental-Design with three phases; phase A (2 weeks) with no treatment, phase B (4 weeks) with LSVT-BIG-treatment and LSVT-BIG-hometraining, and phase C (7-8 weeks) with LSVT-BIG-home-training. Two persons with PD participated. Outcome measures included the Mini-Balance-Evaluation-Systems-Test (Mini-BESTest) with its four subcomponents ("anticipatory postural adjustments", "postural responses", "sensory orientation", "balance during gait"), the Step-Test (ST) and 10-Meter-Walk-Test-fast (10MWT-fast). The participants were assessed 6, 4 and 8 times during phase A, B and C, respectively. During phase B, they received 16 individual 1-hour LSVT-BIG-treatment sessions and completed between 28 and 39 1-hour sessions LSVT-BIG-home-training. During phase C, they were encouraged to complete one session of home-training every day. RESULTS: The Mini-BESTest-total-score, "balance during gait", ST and 10MWT-fast improved significantly in both participants. One participant demonstrated improved "postural responses". Two of the Mini-BESTest subcomponents were not sensitive to possible improvements. CONCLUSION: LSVT-BIG may have a positive effect on dynamic balance and gait-speed in persons with PD.