The effects of three yoga breathing practices were evaluated on performance on a letter-cancellation task which is a left-hemisphere dominant task. The three yoga breathing practices (right, left, and alternate nostril breathing) were selected because unilateral forced nostril breathing stimulates the contralateral hemisphere. There were 20 male volunteers whose ages ranged from 20 to 45 years (M age=28.4 yr., SD=5.7). All subjects were assessed before and after four sessions, i.e., right nostril yoga breathing, left nostril yoga breathing, alternate nostril yoga breathing, and breath awareness as a control. The letter-cancellation task scores were significantly improved, i.e., there were fewer errors following right and alternate nostril yoga breathing (Wilcoxon paired signed-ranks test). The improved performance may be related to the enhancement of contralateral hemisphere function found with selective nostril breathing.