A 44-year-old male patient, diagnosed with HD in 2014, showed slight slowing of rapid alternating movements in the upper limbs and mildly slowed finger tapping on the left side on neurological examination. Chorea and behavioral symptoms were treated with haloperidol (0.5 mg/d), quetiapine (200 mg/d), and citalopram (30 mg/d) at the time of the study. The patient displayed significant deficits in switching of attention (completion time), verbal interference (congruent accuracy, congruent and incongruent reaction time), maze navigation (trials completed, overrun errors, total errors), and emotional identification (accuracy of fear, disgust, and happiness identification) tasks at the baseline clinic visit. He had no desire to stop smoking and continued to smoke ~23 cigarettes/d throughout the study. He self-reported that there had been an incident where he became extremely agitated and kicked the door in week 2; however, this passed quickly and he was unable to recall the cause. No other side effects were reported. Following 4 weeks of varenicline treatment, UHDRS total motor score decreased from 11 to 8. While fine motor task and gait scores showed modest improvement, hyperkinesia and Parkinsonism scores were moderately elevated (Table 1). His UHDRS behavioral subscale increased from 4 to 8, due to the aggressive outburst (Table 2). Cognitive testing at 4 weeks showed significantly improved performance in the switching attention (domain z-score: -4.00 vs -1.7) and verbal interference (domain z-score: -2.95 vs -1.90) tasks. Performance in tests of executive function (domain z-score: -2.82 vs -1.72) and emotional identification (domain z-score: -2.13 vs -1.03) was also significantly improved (Figure 1). He continues to smoke and has reported no further episodes of aggression or irritability.