Purpose: To determine if Tai Chi exercise is effective in improving aerobic capacity. Methods: A computerized search of seven databases was conducted using the mesh term 'Tai Ji', published between January 1, 2000, and June 1, 2007, in order to update a previous meta-analysis examining the effect of Tai Chi on aerobic capacity. Effect sizes (ESs) and 95% confidence intervals were calculated using D-STAT software. The ES for each study was weighted by the sample size and pooled variance. The effects of Tai Chi exercise on aerobic capacity were calculated including study design, gender, age, and type of comparison group. Results: A total of 170 citations were obtained, with 7 new studies meeting the inclusion criteria and added to studies from the previous meta-analysis. Large significant effects of Tai Chi on aerobic capacity were found for subjects enrolled in the cross-sectional studies (ES = 1.33), in both women and men (1.09 and 0.86, respectively), among adults =55 years old (ES = 1.07), and when comparing sedentary subjects with those in Tai Chi exercise groups (ES = 0.99). Small to moderate effects, though nonsignificant, were found for subjects enrolled in the experimental studies (ES = 0.38), adults <55 years old (ES = 0.16), and when comparing subjects participating in other physical activity with those in Tai Chi exercise groups (ES = 0.45). Conclusions: Tai Chi exercise is effective in improving aerobic capacity when practiced long term. Middle-aged and older women and men benefit most, with greater gains seen among those initially sedentary. Tai Chi can be recommended as an alternative aerobic exercise, particularly among sedentary adults ≥55 years old.