Mindfulness is associated with low levels of neuroticism, anxiety, and depressive symptoms, as well as high levels of self-esteem and satisfaction with life (Brown & Ryan, 2003). As part of a 3-month randomized waitlist-controlled trial of the effects of the Transcendental Meditation (TM) program on university students (N=295), we examined the impact of TM practice on mindfulness as measured by the Kentucky Inventory of Mindfulness Skills (KIMS; Baer, Smith, & Allen, 2004). A repeated measures ANOVA on total KIMS scores showed a significant time×treatment interaction, with the TM participants reporting greater increases in mindfulness than the waitlist participants. All KIMS subscales were positively intercorrelated at pretreatment, and there were no differences over time or as a function of treatment condition in subscale intercorrelations. Therefore, previously published findings of a positive correlation between subscales measuring the skills of observing and accepting-without-judgment one's inner experiences only among those with meditation experience may have reflected a self-selection effect rather than a change in the relation of these mindfulness components resulting directly from meditation practice. © 2009 Wiley Periodicals, Inc. J Clin Psychol 65: 1–16, 2009.